Symposium Organizers
Hernan M#65533;guez, Instituto de Ciencia de Materiales de Sevilla
Yi Cui, Stanford University
Kylie Catchpole, The Australian National University
Symposium Support
Aldrich Materials Science
Royal Society of Chemistry
L8: New Materials for Optoelectronics I
Session Chairs
Kylie Catchpole
Hernan Miguez
Thursday PM, December 05, 2013
Hynes, Level 2, Room 200
2:30 AM - *L8.01
3D Deterministic Aperiodic Structures - Transport and Localization of Light
Michael Renner 1 Erik Waller 1 Georg von Freymann 1
1University of Kaiserslautern Kaiserslautern Germany
Show AbstractIntroducing disorder in a controlled way into photonic crystals allows studying the disorder-related change of the underlying transport mechanisms. Recently, controlled disorder has been introduced by mixing different ratios of spheres of different materials and assembling them into fcc opaline photonic crystals [1]. This leads to a random distribution of the defective sites. Here, we introduce deterministic aperiodic disorder in woodpile and cubic photonic crystals. Deterministic aperiodic structures offer the possibility to reproducibly create specific potential landscapes whose Fourier components are determined by the underlying aperiodic sequence. In accordance with Lebesgue&’s spectral theorem the Fibonacci, Thue-Morse and Rudin-Shapiro sequences are examples of the three basic spectral measures, namely pure-point, singularly-continuous and absolutely-continuous, respectively. Especially, the Rudin-Shapiro series is said to be indiscernible from randomly disordered samples concerning their diffraction patterns/properties [2]. Varying the structural parameters, i.e., filling fraction and lattice spacing, according to the aperiodic sequences allows us to introduce deterministic aperiodic disorder into the photonic crystals. Samples are fabricated via direct laser writing in negative-tone photoresist. Using a dip-in lithography approach, samples of considerable height (> 70 unit cells) are prepared with constant high quality throughout the volume. Employing additionally a galvanometric scanning unit, large volumes can be filled, reducing writing times by about two orders of magnitude. After development the samples are characterized with reflectance and time-resolved transport measurements as well as with Laue diffraction. The different types of aperiodic disorder can clearly be discerned in the Laue diagrams. Results from the samples with deterministic aperiodic disorder are compared to such from randomly disordered samples. The different series show characteristic localization behavior, which might be tunable by tailoring the underlying series. Hence, 3D deterministic aperiodic structures could present themselves as interesting materials for electro-optic applications. [1] P.D. Garcia et al., Phys. Rev. A 84, 023813 (2011) [2] M. Baake and U. Grimm, J. Phys. Conf. Ser. 226, 012023 (2010)
3:00 AM - L8.02
Fabrication and Characterization of Metallo-Dielectric Photonic Crystals with Plasmonic Response at Optical Wavelengths
Victoria Chernow 1 Julia Greer 1
1California Institute of Technology Pasadena USA
Show AbstractThe energetic efficiency of current photovoltaic devices suffers from incomplete light trapping. A promising method for achieving enhanced light trapping is the incorporation of 3-dimensional metallo-dielectric photonic crystals into PV devices. We herein present the fabrication methodology and characterization of 3D silver hollow nano-lattices whose hierarchical dimensions span from tens of nanometers in individual strut diameter, to several microns in unit cell size, to hundreds of microns in overall structure extent. The tailored design of hollow Ag nanolattices allows these structures to not only act as 3D waveguides which direct optical mode propagation, but also as surface plasmon coupling structures. Enhancement in light trapping is thus achieved by creating interference between different modes propagating throughout the periodic array, as well as through the excitation of surface plasmon resonances in the metal-dielectric interfaces through absorption of frequencies in the solar spectrum. The novel 3D plasmonic waveguides, or nanotruss lattices, were fabricated utilizing state of the art two photon lithography, followed by plasma sputtering of the plasmonic material, resulting in conformally coated complex silver nanostructures. The core polymer within the nanotruss structures was then selectively etched out, resulting in the creation of silver-air metallo-dielectric photonic crystals.
3:15 AM - L8.03
Direct Transcription of Two-Dimensional Colloidal Crystal Arrays into Large-Area Three-Dimensional Silicon Photonic Crystals
Alexandru Vlad 1 Andreas Froelich 2 Thomas Zebrowski 3 Constantin- Augustin Dutu 1 Kurt Busch 4 Sorin Melinte 1 Martin Wegener 2 Isabelle Huynen 1
1Universite catholique de Louvain Louvain la Neuve Belgium2Karlsruhe Institute of Technology Karlsruhe Germany3Karlsruhe Institute of Technology Karlsruhe Germany4Humboldt University of Berlin Berlin Germany
Show AbstractAmongst the photonic crystals architectures, the 3D design remains the most challenging to fabricate. This originates from the stringent requirements on the constituent materials and the quality of processing. Structuring dielectric materials at the 100-nm scale and with 3D periodicity is not straightforward and several methods have been proposed to address this bottleneck. In this talk, we will discuss a large area 3D structuring strategy for advanced photonic materials by adding the third dimension to 2D etch masks. Surface structuring by nanosphere lithography (NSL) is merged with a novel silicon etching method to fabricate ordered 3D architectures. The SPRIE method, Sequential Passivation Reactive Ion Etching, is a one-step processing protocol relying on sequential passivation and reactive ion etching reactions using C4F8 and SF6 plasma chemistries. Instead of generating smooth and straight etch profiles we have adapted the procedure in such a way that it produces regular size variations in the etch profile. The diffusion of fresh reactants and etch product species inside the etched channels is found to play an important role affecting the structural uniformity of the designed structures and the etch rate drift is corrected by adjusting the reaction times. High quality photonic crystals are thus obtained by adding the third dimension to the 2D colloidal crystal assemblies through SPRIE. Careful adjustments of both mask design and lateral etch extent balance allow the implementation of even more complex functionalities including photonic crystal slabs and precise defect engineering. We demonstrate 3D photonic crystal lattices exhibiting optical stop-bands in the infrared spectral region proving the potential of SPRIE for fast, simple and large-scale fabrication of photonic structures. Numerical modeling based on a structural characterization of the fabricated structures correctly predicts the optical response of the obtained photonic structures [1]. The SPRIE protocol is presently investigated for the realization of tapered structures with axial diameter modulation designed to enhance the light absorption in silicon solar cells or in conductive polymer Schottky junction solar cells [2].
[1] A. Vlad et al., Advanced Functional Materials 2013, 23, 1164;
[2] A. Vlad et al., in preparation.
3:30 AM - L8.04
New Generation of Si-Based Down Converter Layer
Lucile Dumont 1 Yong-tao An 1 Christophe Labbe 1 Julien Cardin 1 Ing-Song Yu 2 Fabrice Gourbilleau 1
1CIMAP/CNRS Caen France2Southern Taiwan University of Science and Technology Tainan Taiwan
Show AbstractIncreasing solar cell efficiency while keeping low cost process is a key issue for the Si solar industry in the next years. One of the solutions consists in developing frequency conversion layer compatible with the Si industry, to absorb and convert one UV photon in two Infra-Red ones. To achieve such a goal, we based our work on the development of a matrix which will be compatible with this PV technology but which should also contain sensitizers to efficiently excite the rare earth ions. The use of sensitizers allows to overcome the low absorption cross-section of the lanthanide ions when they are embedded in glasses. Thus, a SiNx matrix doped with the couple of rare earth ions, Tb-Yb, has been fabricated by reactive magnetron co-sputtering and studied. The first step of this work consists in achieving an intense emission of Tb3+ ions by optimizing the deposition parameters to enhance the coupling between sensitizers and Tb3+. This has been evidenced by deep time resolved- and excitation- photoluminescence experiments as a function of the Tb3+ concentration. The second step has consisted in the incorporation of an increasing content of Yb3+ ions to the optimized Tb-doped matrix with the aim to obtain an intense emission at 980 nm through a non resonant excitation laser line. By a careful analysis of the optical properties of this system, the excitation mechanisms of Tb3+ and Yb3+ ions will be discussed. An internal quantum efficiency as high as ~190% has been achieved. With the aim of always improving the efficiency of such a conversion frequency layer, a plasmonic structure has been added. It consists in depositing a thin silver layer using the same fabrication technique. After a suitable post annealing process, the effect of this metallic layer on the Tb3+, and Yb3+ emissions under laser excitation has been analyzed and the most relevant results obtained such as enhancement of the emission, interaction Plasmon-Emitters, a.s.o. will be presented. Finally, different Si solar prototypes have been fabricated and tested to demonstrate the gain expected in the efficiency of the cell using these two different optimized structures.
3:45 AM - L8.05
Resonant Plasmonic Absorption Processes in Graphene Nanostructures
Victor Watson Brar 1 Min Seok Jang 1 Michelle Sherrott 1 Josue Lopez 1 Harry Atwater 1
1Caltech Pasadena USA
Show AbstractSingle-layer graphene has been shown to have intriguing prospects as a plasmonic material, as modes having plasmon wavelengths sim; 20 times smaller than free space (lambda;p sim; lambda;omicron; /20) have been observed in the 2minus; 6 THz range, and active graphene plasmonic devices operating in that regime have been explored. However there is great interest in understanding the properties of graphene plasmons across the infrared spectrum, especially at energies exceeding the graphene optical phonon energy. We have used infrared microscopy to observe the modes of tunable plasmonic graphene nanoresonator arrays as small as 15 nm. We map the wavevector-dependent dispersion relations for graphene plasmons at mid-infrared energies from measurements of resonant frequency changes with nanoresonator width. By tuning resonator width and charge density, we probe graphene plasmons with lambda;p le; lambda;omicron; /100 and plasmon resonances as high as 310 meV (2500 cm^-1) for 15 nm nanoresonators. In this talk, we also demonstrate how the plasmonic absorption of a graphene sheet is enhanced and perturbed in controllable ways by controlling the thickness and permittivity of the supporting substrate. We will show the results of recent experiments where 20% absorption is achieved in the plasmonic modes of a graphene sheet by carefully selecting the properties of underlying boron nitride and silicon nitride substrates. We also demonstrate how additional absorption pathways can be created by modifying the surrounding dielectric environment to have optical resonances that can couple to the graphene plasmons. These new composite resonances are a versatile tool in expanding the working range of graphene plasmonic devices, as well as exploring the fundamental physics of plasmons in two-dimensional materials. A theoretical model that explains our results has been developed and is used to predict the performance of optically active graphene structures.
4:30 AM - L8.06
Self-Assembly and Optical Properties of Large-Scale Silver and Gold Nanoprism
Mohammad Mehdi Shahjamali 1 Freddy Boey 1 Can Xue 1
1Nanyang Technological University Singapore Singapore
Show AbstractThe self-assembly of mono-disperse inorganic nanoparticles into highly ordered arrays represents an exciting route to advanced materials with novel functions. It allows programming their properties by changing the size, shape, composition and packing order of the assemblies. While substantial progress has been achieved in the fabrication of superlattices with isotropic building blocks, limited advances have been made with anisotropic building blocks.
In this article, we report the controlled growth large-scale, monolayered Au and Ag nanoprism superlattice by polymer ligands in an entropy-driven interfacial self-assembly process. Furthermore, a 3-dimensional finite element method was used to investigate the plasmon resonance properties for individual nanoprisms in different dielectrics and plasmon coupling in nanoprism aggregates. Scattering enhancement of more than 10x has been observed experimentally with these nanoprism nanosheets.
Our rapid and simple strategy may be extended to other anisotropic plasmonic building blocks, offering a robust and inexpensive avenue to plasmonic nanosheets for various applications such as nanophotonic devices, biochemical sensing, optical processing and solar photovoltaics.
4:45 AM - L8.07
Reaching Theoretical Resonance Quality Factor Limit in Coaxial Plasmonic Nano Resonators Fabricated by Helium Ion Lithography
Mauro Melli 1 Aleksandr Polyakov 1 Daniel J. Gargas 1 Choung Huynh 2 Larry Scipioni 2 Wei Bao 1 David Frank Ogletree 1 Peter James Schuck 1 Stefano Cabrini 1 Alexander F Weber-Bargioni 1
1Molecular Foundry LBNL Berkeley USA2Carl Zeiss Microscopy LLC Peabody USA
Show AbstractWe demonstrate that it is possible to fabricate optical antennae that match the theoretically predicted resonance quality factor for a flawless antenna structures using helium ion lithography (HIL).
The concept of optical antennae has revolutionized the field of nano optics and allows in principle to manipulate and control light with a single digit nano meter resolution. This development has been made possible due to recent accomplishments in nanofabrication that has permitted structuring materials such as Au, Ag or Al with single digit nm resolution to enable plasmonic coupling between nano antennae. Hence, much of the work has been dedicated to reproducibly fabricate optical resonators with a nanometer precision using state of the art fabrication techniques such as Focused Ion Beam (FIB) milling, Electron Beam (e-beam) Lithography, and Induced Deposition Mask Lithography. However, due to the fabrication resolution limitations of > 10 nm, the optical properties of plasmonic antenna fall short of their theoretical predicated resonator quality factor and enhancement factors. Geometrical deviations from the ideal geometry - such as tapering, sidewall roughness, and corner rounding on length scales comparable to the SPP skin depth are the reasons for the shortcomings of actual optical antennae compared to their theoretical model structure.
In this work, we fabricated coaxial optical antennae by using Helium Ion Lithography (HIL) that allows the fabrication of coaxial optical antennae with reproducible gap sizes of 8 nm, perfectly parallel sidewalls and edges with radii of curvatures of less than 4 nm. Wavelength dependent transmission measurements are used to determine the resonance peak and the resonance quality factor then compared to the theoretical response of an ideal geometry, determined by a numerical Finite Difference Time Domain (FDTD) simulation. We found a very good match between the experimental values and the simulated resonances of perfect structure.
For comparison, coaxial antennae with 30 nm critical dimensions were fabricated using both HIL and the more common Ga Focus Ion Beam lithography (Ga-FIB). The quality factor of the Ga-FIB resonators was 60% of the ideal HIL results for the same design geometry due to limitations in the Ga-FIB fabrication process. In summary, we demonstrate that it is possible to fabricate coaxial optical antennae that match the theoretically predicted resonance quality factor for flawless structures using helium ion lithography (HIL).
5:00 AM - L8.08
Growth, Spectral Response, and Nonlinear Optical Enhancements of Hybrid Nanogap-Antennas
Blake Simpkins 1 James Long 1 Igor Vurgaftman 2
1Naval Research Laboratory Washington USA2Naval Research Laboratory Washington USA
Show AbstractNanogap hybrid antennas, consisting of two metal nanostructures joined by a gap material serving as an impedance load, can utilize optical-frequency resonances for enhanced collection and localization of optical fields. These structures have been identified as potential building blocks for optical analogs to RF circuit elements with applications in sensing, photovoltaic energy conversion, single photon sources, and optical communication.
Using electrochemical deposition into alumina templates, we have fabricated and characterized nanogap antennas comprising two Au nanorods (with individual rods ranging from 105 to 130 nm in length) joined by a CdS-filled ~40-nm gap, with a uniform diameter of ~65 nm. Antennas were dispersed on ITO and individually characterized with polarization-dependent, wavevector-resolved dark-field microspectroscopy and imaging, which revealed three distinct optical resonances: a longitudinal mode that resonates with a peak response ~950 nm, and two nearly degenerate transverse modes that are split by substrate interactions. A strong, out-of-plane, transverse mode peaks near 570 nm which is red-shifted compared to a weaker in-plane resonance near 540 nm.
The nonlinear response of the antennas was probed by measuring the second harmonic generation (SHG) of a ~100-fs pulsed pump-beam tuned to the longitudinal resonance. Polarization studies found that the SHG intensity strongly peaked when the incident polarization was aligned with the nanoantenna long axis. These experimental results are consistent with finite-difference time-domain (FDTD) simulations which show the magnitude of the electric field in the gap material is ~an order of magnitude larger when the system is excited under longitudinal polarization as compared to transverse excitation. Simulations also accurately predict the measured longitudinal resonant-wavelength, which is found to be that of a single arm with a slight gap-dependent redshift. For nanogap antennas with asymmetric arms, the overall resonance is localized on the longer of the two arms with the gap fields shifted towards the longer arm.
5:15 AM - L8.09
InGaBiAs:Si as a New Candidate in Near-Infrared to Mid-Infrared Optoelectronics
Yujun Zhong 1 Pernell Dongmo 1 Liang Gong 1 Stephanie Law 2 Bruce Chase 1 Daniel Wasserman 2 Joshua Zide 1
1University of Delaware Newark USA2University of Illinois Urbana Champaign Urbana USA
Show AbstractWe report on a new candidate for near-infrared (near-IR) to mid-infrared (mid-IR) optoelectronics and transparent contacts: InGaBiAs films grown by molecular beam epitaxy (MBE). Near-IR and mid-IR optoelectronic devices cover a broad range of functionality including free space optical communication, environmental gas monitoring and thermal imaging, and many of these devices are based on an InP platform. Dilute bismuthides (i.e. III-V semiconductors containing small amounts of bismuth in the alloy) are a relatively new class of materials which possess many interesting properties. Our group have systematically studied the growth conditions and the potential applications of InGaBiAs on InP substrate1-3. Incorporating bismuth will cause valence band anticrossing (VBAC) and effectively reduce the bandgap. Tuning the composition of InGaBiAs can make it lattice-matched to the InP substrate. Upon further investigation, we found that degenerately doped InGaBiAs:Si are ideal candidates for near-IR and mid-IR transparent contact materials. They are highly transmissive and conductive.
We have experimentally and theoretically demonstrated that the bandgap of undoped InGaBiAs is effectively reduced with the increase of the Bi concentration at a rate around 56meV/Bi%. The longest wavelength we have achieved so far is 2.7 mu;m. We have also demonstrated that degenerately doped InGaBiAs:Si are highly transparent in the infrared range with the exact transparency windows determined by the material's carrier concentration. Degenerately doped InGaBiAs:Si has been demonstrated to be a highly conductive semiconductor (up to 4850 S/cm) due to its high carrier concentration and good mobility.
In conclusion, we have investigated the effective bandgap of undoped InGaBiAs and demonstrated the VBAC both experimentally and theoretically. We also studied the transmittance and conductivity of degenerately doped InGaBiAs:Si films, and demonstrated that they are highly transparent and conductive in the near-IR to mid-IR range. Therefore, InGaBiAs is potentially an ideal candidate for near-IR to mid-IR optoelectronic materials.
1 J. P. Petropoulos, Y. Zhong, and J. M. O. Zide, Applied Physics Letters 99, 031110 (2011).
2 Y. Zhong, P.B. Dongmo, J.P. Petropoulos, and J.M.O. Zide, Applied Physics Letters 100, 112110 (2012).
3 P. Dongmo, Y. Zhong, P. Attia, C. Bomberger, R. Cheaito, J.F. Ihlefeld, P.E. Hopkins, and J. Zide, Journal of Applied Physics 112, 093710 (2012).
5:30 AM - L8.10
Widely Electrically Tunable Metal-Graphene Metasurfaces with Nanoscale Response Times
Yu Yao 1 Mikhail Kats 1 Raji Shankar 1 Yi Song 2 Jing Kong 2 Marko Loncar 1 Federico Capasso 1
1Harvard University Cambridge USA2MIT Cambridge USA
Show AbstractGraphene is emerging as an optical material which can be dynamically tuned by electrostatic doping. However, integration of graphene into optical and optoelectronic devices is limited due to its small thickness and the resultant weak interaction with light. By combining metal and graphene in a hybrid plasmonic structure, it is possible to enhance graphene-light interaction and thus achieve in situ control of the optical response.
Finite-difference time-domain (FDTD) simulation was used to design the hybrid plasmonic structure and understand the coupling between the plasmonic modes of the metallic antennas and the graphene. In our experiment, a CVD (chemical vapor deposition) single layer graphene was first transferred onto 30 nm silicon oxide layer on doped silicon substrate. Gold plasmonic structures were patterned onto the graphene sheet using electron beam lithography. Reflection spectra were taken at various gate voltages using a Fourier transform infrared (FTIR) spectrometer equipped with a mid-infrared microscope. A maximum wavelength tuning range of ~1100 nm (18% of the resonance frequency) is achieved experimentally from the hybrid metal-graphene plasmonic structure at mid-infrared (MIR) wavelengths (6-7 µm). The time response of the device was characterized by measuring the modulation depth of the optical reflection (The incident light is from a continuous wave quantum cascade laser.) for different gate voltage modulation frequencies. Our device exhibits a response time of < 25 ns, which can be further decreased to the picosecond scale by minimizing the contact pad sizes and increasing the insulator thickness underneath the contact pad. Further experiment will be carried out to improve the tuning effect and decrease the response time.
This study confirms that hybrid metal-graphene structures are promising elements for high speed electrically controllable optical and optoelectronic devices.
L9: Poster Session
Session Chairs
Kylie Catchpole
Hernan Miguez
Thursday PM, December 05, 2013
Hynes, Level 1, Hall B
9:00 AM - L9.01
Low Temperature Growth of High Crystallinity GeSn on Amorphous Layers for 3D Photonic Integration and Tandem Solar Cells
Haofeng Li 1 Jeremy Brouillet 1 Alan Salas 1 Xiaoxin Wang 1 Jifeng Liu 1
1Dartmouth College Hanover USA
Show AbstractBecause of its desirable optoelectronic properties, compatibility with Si electronics and lattice matching with III-V semiconductors, Ge has found important applications in advanced optoelectronics such as Si-based electronic-photonic integration and high-efficiency tandem solar cells. Growing high crystallinity Ge on amorphous materials at low temperatures <500 oC can potentially enable 3D electronic-photonic integration on Si as well as low-cost tandem cells on Ge/glass virtual substrates, yet it still remains a significant technical challenge. Here we demonstrate that, by incorporating Sn into Ge to enhance crystallization through the Ge-Sn eutectic system and to modify the band structure towards a direct gap semiconductor, we manage to achieve high crystallinity GeSn thin films on amorphous SiO2 layers at low crystallization temperatures of 340~464 oC, and significantly improved optoelectronic properties simultaneously. The crystallization temperature decreases significantly with the increase of Sn composition in the as-deposited GeSn thin films. A highly (111) textured Ge0.92Sn0.08 thin film with large grain sizes up to tens of microns was achieved from a 9.5% as-deposited Sn composition, as revealed by both X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). EBSD also shows that the average crystal grain size is >5 microns, and that the grain boundaries are mostly twin boundaries and low-angle boundaries, which greatly reduces defect recombination centers. The large grains and the dominance of twin/small angle grain boundaries are due to an extraordinarily large spacing of 0.1~1 mm between nucleation centers from which GeSn grains grow radially, orders of magnitude larger than that in regular solid phase crystallization in semiconductor thin films. This striking observation indicates an exceedingly high lateral growth rate vs. a low nucleation rate in the eutectic-mediated crystallization process of GeSn. Furthermore, by fabricating nano-tipped tapered structures, nucleation is controlled to take place at the tip from which the single crystal grain grows subsequently, demonstrating a promising potential for GeSn single crystal growth on amorphous layers. Another remarkable feature is 8% Sn is incorporated into the Ge lattice, well above the equilibrium solubility limit of ~1%. Correspondingly, the direct band gap optical absorption edge is extended to lambda;=2500 nm (~0.5 eV), right on the verge of indirect-to-direct gap transition. For photonic integration, this transition greatly enhances photonic device performance. For tandem solar cells, this extension in optical response leads to more energy conversion from the infrared spectrum. This Sn-assisted crystallization process is free from common issues related to metal induced crystallization (MIC) such as deep-level defect centers or undesirable heavy doping. It not only offers higher throughput, but also strongly enhances optoelectronic properties due to GeSn alloying.
9:00 AM - L9.02
Computationally Efficient and Intuitive 1D Analytical Model for 3D Metal-Clad Nanocavities
Zheng Li 1 Myung-Ki Kim 1 Kun Huang 1 Hyuck Choo 1
1California Institute of Technology Pasadena USA
Show AbstractWe demonstrate a computationally efficient and intuitive one-dimensional (1D) analytical model that significantly expedites the design and analysis of three-dimensional (3D) metal-clad nanocavities (MCNs) for various nanophotonics applications. The proposed approach is two orders of magnitude faster than a full 3D finite-difference-time-domain computation. Our 1D approach accurately predicts core cavity parameters including resonant frequencies and quality (Q) factors; quickly reveals tradeoffs between different design choices; and serves as a powerful tool with which to optimize the design of 3D MCNs. The configuration of the examined rectangular 3D MCNs includes a metal-coated, infinitely long, low index dielectric layer (or cladding) with an embedded nanocavity consisting of high index dielectric rectangular cavity core centered on the major axis and two slender posts protruding out of the core along the same axis and in the opposite directions. In our approach, we break down the 3D analysis into 2D and 1D tasks. Using the numerically calculated modal properties of the cavity&’s 2D cross-section, we develop a 1D analytical solution along the major axis (this is analogous to the well-known 1D finite potential well problem). Because the MCNs&’ 2D cross-sections exhibit four-fold symmetry, we investigate the antisymmetric-antisymmetric transverse-electric-like mode that yields a maximum photonic band gap. The high index nanocavity core supports the targeted mode, while the two post regions along the major axis outside the cavity core exhibit a near-zero refractive index and provide confinement. Consuming less than 1/100th of the full 3D computation time, the 1D model predicts the resonant frequencies within a 4% deviation for wavelengths from 1.1 to 1.6 mu;m and the Q factors within 10% by considering the metallic loss in the nanocavity. When the length of the nanocavity core along the major axis decreases to the dimensions of its 2D cross-section, our 1D model overestimates the Q factors. A closer examination of the metallic loss at this condition reveals that multimode effects caused by the presence of additional discontinuous interfaces in the 3D geometry become significant and generate additional loss uniformly distributed along the major axis; these further reduce Q-factors below the values predicted by our 1D model. We have also examined the case in which the post regions have finite lengths and one of the regions ends with a metal contact. We discover that tuning the lengths allows us to control the magnitude of the radiation loss, and to keep the influence of the metal contact negligible on the cavity properties. Furthermore our study elucidates the underlying physics that relates the mode inside the cavity, its far-field patterns, and its coupling efficiencies with integrated waveguides. We will present the capabilities and limitations of our 1D approach for the design and analysis of 3D MCNs in nanophotonic applications.
9:00 AM - L9.03
Thermophotovoltaics: 2D Metallic Photonic Crystals for Combined Light Trapping, Ohmic Contact, and Antireflective Coating
Corey Shemelya 1 2 Dante DeMeo 2 Ganesh Balakrishnan 3 Tomas Rotter 3 Thomas Vandervelde 2
1University of Texas at El Paso El Paso USA2Tufts University Medford USA3University of New Mexico Albuquerque USA
Show AbstractA two dimensional metallic photonic crystal pattern with the addition of a SiNx ARC have been previously shown through simulations to increase the optical intensity within an active PV diode region; increase the photon/exciton interaction time; and decrease the number of recombination events. The simulated PhC implied a TPV cell with a greater over all conversion efficiency, as well as, a larger external quantum efficiency and internal quantum efficiency. This work experimentally demonstrates the enhancing effect of the metallic PhC on the diode stage of a Gallium Antimonide (GaSb) TPV device
Thermophotovoltaic generators have traditionally been composed of three parts (emitter, filter, diode) which convert infrared photons into an electrical current.[1] Present research in TPV devices demonstrate maximum conversion efficiencies of only around 20%.[2] However, theory predictions that total system efficiencies of 30-40% can be reached. [2] . In order to reach this limit, our research demonstrates that 2D PhC patterns can be successfully implemented as a TPV filter stage offering many benefits over current filter stage technologies. This is a new application of PhC in the field of TPV as present reseach only utilizes 2D PhC patterns for the Emitter stage. The focus of this research to increase the efficiency of the Gallium Antimonide (GaSb) TPV cell, through the use of a two dimensional metallic photonic crystal filter. Metallic 2D PhC have yet to be implemented into TPV filter stages and may provide many benefits over traditional 1D PhC filters. These benefits include narrower spectral responses and the ability to act as both a filter and a front side contact increasing the TPV diode surface area and thereby power out.
A photonic crystal was first designed and optimized in Lumerical FDTD to create a PhC standing wave corresponding to the bandgap of GaSb. It was determined that the addition of a PhC pattern increased photon absorption by The PhC cavity by 66% and the addition of SiNx as an ARC increased absorption by 80%. The PhC was fabricated from ohmic contact materials resulting in a decreased path length for excitons and therefore a decreased number of potential recombination events. Optical characterization of the metallic PhC patterns demonstrates ARC properties as well as an enhancement in generated electrical current (17%) which may allow the metallic PhC to replace standard TPV contacts as well as traditional ARC coatings.
[1] Nelson, Robert E., “A brief history of thermophotovoltaic development”, Semicond. Sci. Technol. 18 S141, 2003.
[2] Mauk, Michael G. “Survey of Thermophotovoltaic (TPV) Devices,” Mid-infrared Semiconductor Optoelectronics, Springer Berlin / Heidelberg, 2006 (pg 674).
9:00 AM - L9.05
Diffraction Gratings Patterned on Titania Electrodes for Enhance Light Harvesting in Dye Solar Cells
Carmen Lopez Lopez 1 Silvia Colodrero 1 Hernan Miguez 1
1Instituto Ciencias de Materiales CSIC-US Sevilla Spain
Show AbstractDifferent optical designs of Dye Solar Cell (DSC) have been successfully employed to trap light in the active layer with the aim of improving power conversion efficiency.[1,2] Here, 1D and 2D relief gratings are patterned onto the surface of nanocrystalline titania electrodes using a combined soft-lithography and microcontact printing approach.[3] This method gives rise to an increase in the photocurrent of the cell as a result of the angularly back diffracted of selected wavelengths. The integration of such surface patterned electrodes shows promising photovoltaic performance enhancement of the cells.
References
1. F.E.Gálvez, E.Kemppainen, H.Míguez, J.Halme, J.Phys.Chem., 2012, 116, 11426.
2. S. Colodrero, A. Forneli, C. Loacute;pez-Loacute;pez, L. Pellejagrave;, H. Míguez, E. Palomares, Adv. Funct. Mater. 2012, 22, 1303.
3. D. Quin, Y.Xia, G.M. Whitesides, Nature protocols, 2010, 5, 491.
9:00 AM - L9.06
Direct Writing of 3D Polymer Photonic Crystals for the Visible Spectrum Using Resist and Dose Modulated 3D Electron-Beam Lithography
Alexandru Vlad 1 Andreas Froelich 2 Thomas Zebrowski 3 Patrice Brenner 4 Kurt Busch 5 Sorin Melinte 1 Martin Wegener 2
1Universite catholique de Louvain Louvain la Neuve Belgium2Karlsruhe Institute of Technology Karlsruhe Germany3Karlsruhe Institute of Technology Karlsruhe Germany4Karlsruhe Institute of Technology Karlsruhe Germany5Humboldt University of Berlin Berlin Germany
Show AbstractIn this talk, the fabrication and characterization of 3D polymer photonic crystals using high resolution and high-energy electron beam lithography is presented. A novel type of resist and dose-modulated electron beam lithography (RDM-3D-EBL), extensively exploiting the intrinsic properties of resist-electron beam interaction is detailed. In the RDM-3D-EBL method, orthorhombic 3D polymer photonic crystals are obtained by a single exposure of a multilayer PMMA/MAA resist stack to a high-energy electron beam. Depending on the local exposure dose, either one or both of the resists are removed during a subsequent development step. 3D photonic structures can thus be produced in a single exposure step. During this step the periodicity and feature size in the z-direction are controlled by the resist layer thickness. The feature size and periodicity in the x-y-plane can be determined by the patterning step and the development conditions. The correct parameters for the EBL processing and the development step were found to be strongly dependent on the exposure energy, substrate type and pattern density and were calibrated accordingly. The theoretical prediction of electron trajectories in the resist multilayer realized using a Monte Carlo simulation code (CASINO) will be discussed [1]. While the realized structures have orthorhombic crystal symmetry, we will also discuss the implementation of other crystal symmetries. Extensive structural characterization by FIB cross-section analysis is combined with numerical modeling to correlate the measured optical response with theoretical predictions. The fabricated polymer photonic crystals display tailored photonic stop bands in the visible spectrum range. The stop band position is adjusted by morphology correct choice of the photonic crystal geometry. Nearly the entire visible spectrum range is thus accessed by simply adjusting the multilayer resist stack exposure dose. In conclusion, we show how photonic crystals with precise size and positioning as well as predefined optical stop-bands can be realized simply using a single-step, direct write electron-beam lithography protocol. An on-chip graded band-stop filter has been realized by direct writing of a chirped photonic crystal structure through dosed irradiation of the multilayer stack. This can lead to ultimate miniaturization of on-chip integrated photonic crystal based spectrophotometers [2].
[1] A. Vlad et al. Nano Letters 2009, 9, 2838; P. Jedrasik et al. J. Nanosci. Nanotechnol 2011, 11, 8924.
[2] A. Froelich et al. in preparation.
9:00 AM - L9.07
Effect of Surface Modified Silica Layer on Silver Nanoparticle in Organic Photovoltaic (OPV) Cells
Joohyun Lim 1 Woochul Lee 1 Jong-In Hong 1 Jin-Kyu Lee 1
1Seoul National University Seoul Republic of Korea
Show AbstractMetal nanoparticles have been very attractive materials owing to their particular character: Localized surface plasmon resonance and scattering for improving light harvesting ability in photovoltaic cells. In this regard, many researchers have reported that metal NPs are introduced to increase the performance of bulk-heterojunction (BHJ) solar cells as an additive without changing the thickness of active layer. However, it is necessary to modify the surface of metal nanoparticles for preventing aggregation of each particles and photo-induced charge trap. Very recently, introduction of silica layer and surface modification on the metal nanoparticles was tried. However, the effect of the silica layer and the morphology of active layer (BHJ) with nanoparticles were not sufficiently understood yet.
We prepared the silver nanoparticles having silica coating layer modified with oligo-thiophene (OT) (Ag@SiO2@OT NPs), which were well dispersible in organic solvent and showed good miscibility with poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) (P3HT:PCBM) composite films. The performance of the photovoltaic devices based on the active composition of P3HT:PCBM was improved in terms of the light harvesting ability and photo conversion efficiency value when Ag@SiO2@OT NPs were incorporated, comparing to the cases of pristine P3HT:PCBM device as well as nanocomposite devices with bare Ag nanoparticles. Serious problem of Voc drop, when the concentration of bare Ag NPs was increased, was not observed in the case of nanocomposite devices with Ag@SiO2@OT NPs. Furthermore, the location of Ag@SiO2@OT NPs in the nanocomposite devices could be confirmed as mainly distributed within P3HT domain, by TEM experiments after selective removing of PCBM region. Details including synthetic method, characterization of morphology of active layer, and the result of surface modification will be discussed during the presentation.
9:00 AM - L9.09
Graded Refractive Index Anti-Reflection Coatings for Organic Substrates via Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation (RIR-MAPLE)
Ryan D. McCormick 1 Ayomide Atewologun 1 Weidong Zhou 2 Adrienne D. Stiff-Roberts 1
1Duke University Durham USA2University of Texas at Arlington Arlington USA
Show AbstractAnti-reflection (AR) coatings for flexible, organic substrates require organic-based materials with well-matched coefficients of thermal expansion that will not crack or delaminate, as do traditional AR materials designed for inorganic substrates. While quarter- and half-wave plates can reduce reflection at specific wavelengths, graded refractive index (GRIN) coatings are desirable because they offer AR properties across a broad spectral band and for a wide range of incident angles. One approach to achieve a GRIN coating is to continuously vary the porosity of an AR polymer film such that the refractive index is reduced from that of the substrate to that of air over a given thickness [1]. In order to fabricate such a coating, it is critical to co-deposit a polymer blend (AR polymer and porogen polymer) with isotropic nanoscale phase domains (< 40 nm). In this way, the AR coating behaves as an effective medium without light scattering across the visible spectrum. Yet, solution-based co-deposition of polymers often leads to micron-sized domains that are too large to prevent light scattering in the visible spectrum. Furthermore, layering of solution-cast films is difficult because of the inevitable dissolution of existing layers by repeated deposition of polymers with similar solubility.
A novel deposition technique known as resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) has demonstrated nanoscale pore sizes suitable for the visible spectrum [2]. RIR-MAPLE, which is a gentle offshoot of pulsed laser deposition, has been developed to deposit one or more organic materials as thin films regardless of solubility. Importantly, RIR-MAPLE can actively control the polymer blend ratio during deposition to create the graded structure required for the GRIN coating. In this work, we will present the application of RIR-MAPLE to depositing styrene (AR polymer)/methyl methacrylate (porogen polymer) blends for the fabrication of organic GRIN AR coatings that are appropriate for polycarbonate substrates, and eventually, organic optoelectronics. In particular, RIR-MAPLE target chemistry, substrate temperature, and post-deposition surface treatment will be investigated. Scanning electron microscopy will be used to characterize phase domains in the porous structures. Optical characterization of the films, via integrating sphere reflection/transmission/absorption measurements, will demonstrate the reduction in reflectance achieved by such coatings across the visible spectrum. While porous polymer films with a graded material structure are nearly impossible to create with solution-casting methods, this work will demonstrate that RIR-MAPLE can enable these structures for application to GRIN AR coatings.
[1] X. Li, J. Gao, et al., Advanced Functional Materials, vol. 20, pp. 259-265, 2010.
[2] R. D. McCormick, E. D. Cline, et al., Proc. SPIE 8258, Organic Photonic Materials and Devices XIV, p. 825806, 2012.
9:00 AM - L9.100
Energy Level Tailoring of Diketopyrrolopyrrole-Based Small Molecules for Organic Field-Effect Transistor and Solar Cell Applications
Won Sik Yoon 1 Sang Kyu Park 1 Illhun Cho 1 Soo Young Park 1
1Seoul National University Seoul Republic of Korea
Show AbstractAmong many π-conjugated organic semiconducting building blocks, diketopyrrolopyrrole (DPP) has attracted significant attention due to their structural compactness, driven by strong πminus;π stacking in the solid state, their quasi-planar backbone structures, and the facile control over the MOs, which cooperatively yield outstanding charge carrier transport efficiencies in organic photovoltaics (OPVs) and organic field-effect transistors (OFETs). In particular, DPP-based small molecules are attracting keen interest due to their inherent advantages over polymeric analogues, such as perfectly defined chemical structure, easy purification and reproducibility without batch to batch variation.
In this work, we have synthesized a new series of small molecules comprising DPP backbone for organic electronic device applications. The frontier molecular orbitals in these series are elaborately tuned by introducing a strong electron-accepting functionality (dicyanovinyl) and various thiophene containing electron-donating units. Among these DPP-based small molecules, thiophene and dicyanovinyl-substituted DPP-based organic semiconductor, DPP-T-DCV, exhibited an outstanding electron mobility of up to 0.96 cm2 V-1 s-1 in solution-processed single-crystal OFETs (SC-OFETs). Furthermore, by replacing the thiophene moiety to more strong electron-donating unit, we could effectively control the frontier energy levels to demonstrate ambipolar transistors. With such precise energy level tailoring, together with the solubility control and molecular structure engineering, we could realize highly efficient small molecule OPVs as well.
9:00 AM - L9.102
Effect of Single Nanoparticle Gap Modes on the Optical Properties of Conjugated Polymer Thin Films
Binxing Yu 1 Jeseph Woo 2 Michael Kong 2 Deirdre O'Carroll 1 2 3
1Rutgers University Piscataway USA2Rutgers University Piscataway USA3Rutgers University Piscataway USA
Show AbstractImproving light-harvesting in ultra-thin conjugated polymer active layers is an ongoing topic of interest in organic photovoltaics community. In recent work, we have shown that metal-polymer nanoheterostructures consisting of Au plasmonic nanoantennas coupled to a sub-50-nm poly(3-hexylthiophene) (P3HT) layers on a metallic ground plane are a promising solution to this issue [1]. The plasmonic nanoantennas are capable of concentrating and enhancing optical fields within deeply-subwavelength regions of the P3HT active layer due to strong coupling between localized surface plasmon resonances supported by the nanoantennas and free electron oscillations in the adjacent metallic plane. On resonance, the incoming light field is greatly amplified in the nanometric P3HT “gap” between the nanoantenna and the metal plane, an effect that is predominantly attributed to plasmonic gap modes resonances (i.e., hybridization between localized plasmon modes of the nanoparticle (NP) and the propagating plasmon modes of the metal substrate). Such significantly enhanced electric fields are of vital importance to optoelectronic devices for improving light absorption in the active layer..
Recent theoretical work has highlighted the strong dependence of gap modes resonances upon conditions such as the shape and size of nanostructures, dielectric properties of the environment as well as the substrate and the distance between NP and the substrate [2]. Here, we fabricated a metal NP/poly(3-hexylthiophene)/metal thin film system to experimentally study the absorption enhancement due to single-nanoparticle gap modes in ultra-thin conjugated polymer films. The conjugated polymer film is less than 50 nm thick and is inserted in the gap region between NP and metallic plane to take advantage of the highly intensified near field. We aim at seeking experimental validation and identification of how the gap mode wavelength, intensity and degree of light localization can be optimized by changing factors such as: gap thickness, nanoparticle height, material type, incident field polarization. Single-particle dark-field spectra obtained from this geometry reveal the shift of the scattering peak originating from highly confined gap modes at the interface due to variation of the geometric parameters of the system. This experimental work seeks to systematically elucidate the effects of gap modes resonances on the optical properties of conjugated polymer thin films which will be constructive in understanding and utilization of gap modes resonances in optoelectronic device fabrication.
1. Yu, B.; Goodman, S.; Abdelaziz, A.; O&’Carroll, D.M.; Light-management in ultra-thin polythiophene films using plasmonic monopole nanoantennas, Appl. Phys. Lett., 101, 151106 (2012)
2. Hutter, T.; Elliott S.; Mahajan S., Interaction of metallic nanoparticles with dielectric substrates: effect of optical constants, Nanotechnology 24, 035201 (2013).
9:00 AM - L9.106
Frequency Selective Emission Using Surface Modification of Photonic Crystals
Saumya Sharma 1 Manoj K Ram 1 Yogi Goswami 1 Elias (Lee) Stafanakos 1
1University of South Florida Tampa USA
Show AbstractA hybrid photonic crystal structure is designed to modify thermal emission spectrum tailored to suit applications in biosensors, detectors and thermophotovoltaic devices [1]. The hybrid photonic crystal structure uses the effect of surface morphology on the optical properties to introduce the selectivity in frequencies for the emission. The thermal emission in a certain set of frequencies can be suppressed while allowing the crystal to emit radiation limited in a narrow band of frequencies.
The emission spectrum tunability has been confirmed by using experimental setup as well as theoretical calculations. A metal-dielectric composite with the top metal surface etched into sub wavelength nanostructures is made the base case for the emitter design. From thereon, various periodic arrays of rectangular or circular holes as well as gratings were introduced in the base case [2-3]. While simulating the emission spectrum different metals including Silver, Gold, Tungsten, Nickel and Platinum were considered. Also, changing the dielectrics with varying indexes was also seen to impact the shape of the emission spectrum. Effect of etch depth in such periodic structures was also taken into account. Variations in period of the array and the dimensions of each hole were also noted to affect the narrowness of spectrum. Such frequency selectivity can be attributed to phenomena including Surface Plasmon Polariton (SPP) coupling as well as diffraction by the grating structure [4].
References:
1. M. U. Pralle, N. Moelders, M. P. McNeal, I. Puscasu, a. C. Greenwald, J. T. Daly, E. a. Johnson, et al. Applied Physics Letters 2002, 81 (25), 4685.
2. A. Heinzel, , V Boerner, A Gombert, B Bläsi, V Wittwer, and J Luther, 2000.” Journal of Modern Optics 2000, 47 (13) 2399-2419.
3. H. Sai and Y. Kanamori, Microscale Thermophysical Engineering 7 2003, 101-115.
4. H. Sai, Y.i Kanamori, and H.Yugami. 2005. “Journal of Micromechanics and Microengineering 3003, 15 (9) S243-S249.
9:00 AM - L9.107
Low Temperature Optical Properties of Silver Films
Sriharsha V. Jayanti 1 2 Jong Hyuk Park 1 2 Alexandr Dejneka 3 Dagmar Chvostova 3 Xiaoshu Chen 4 Sang-Hyun Oh 4 David J. Norris 1
1ETH Zurich Zurich Switzerland2University of Minnesota Minneapolis USA3Institute of Physics, ASCR Prague Czech Republic4University of Minnesota Minneapolis USA
Show AbstractDespite the ability of plasmonic metals to confine and manipulate optical energy at the nanoscale, plasmonic studies in the visible are limited by significant ohmic losses at room temperature. By lowering the temperature, we observed moderate to large reductions in ohmic losses on optically thick silver films. We report dielectric constants in the visible obtained from ellipsometry measurements at various temperatures down to liquid helium temperatures, and tabulate the relevant Drude parameters. Furthermore, the temperature dependence of the dielectric constants is strongly influenced by the roughness and crystallinity of the silver surface. Ultrasmooth, single-crystalline silver films showed the largest temperature-dependent improvements whereas rough, polycrystalline films showed little enhancement. Below 50K, the surface plasmon polariton propagation lengths on single-crystalline films were enhanced by 30% at 500 nm to 55% at 750 nm compared to those at room temperature. In rough, polycrystalline films, losses are dominated by the temperature-independent scattering from the roughness and grain boundaries, so very small improvements were observed.
9:00 AM - L9.108
Electrode-Embedded Few-Mode Electro-Optic LiNbO3 Fiber
Jimmy Wang 1 Yung-Hsin Tseng 1
1National Sun Yat-sen University Kaohsiung Taiwan
Show AbstractElectrode-embedded few-mode single-crystal electro-optic (EO) LiNbO3fiber (FMELiOF) with silica glass cladding and In2O3-SnO (ITO) electrode embedded between core and cladding with one-step process by CO2 laser heated pedestal growth (CO2-LHPG) technique is demonstrated.
A half-wave voltage (Vπ) of 4.5 V, effective electro-optic coefficient of 29.0 pm/V and transmission loss of 0.92 dB/cm are achieved in the FMLiEOF with the core diameter of 5 mu;m, electrode distance 20 mu;m, ITO thickness of 300 nm, and overall diameter of 125 mu;m.
A technical comparison of this new type of LiNbO3 EO fiber waveguide against conventional LiNbO3 planar waveguide and its new potential applications will be presented.
9:00 AM - L9.109
Distance-Dependent Fluorescence in Metal-Dye Core-Shell Systems
Thomas Lerond 1 Zackaria Mahfoud 2 1 Davy Gerard 1 Jerome Plain 1 Mathieu Kociak 2
1LNIO Troyes France2LPS Orsay France
Show AbstractThe research of highly luminescent, chemically stable and photostable emitters is one of the workhorses of hybrid plasmonics. The hybrid architecture based on a metallic core surrounded by a luminescent shell is one of the most popular. From the fundamental point of view, a deeper understanding of the energy transfer at the nanoscale is needed to increase the properties of such hybrid nanoobject. Particularly, the distance between the metal core and the active media is one of the key parameters.
In this work, we present a systematic study of the behavior of core-shell (Ag@polyelectrolytes) systems with a layer doped by rhodamine 6G (Rh6G) when the Rh6G is really close to the metallic shell (typically less than 15nm).
The core-shells are based on metal nanoparticles (NPs) synthetized by citrate reduction [1]. Then the shell is made by layer-by-layer deposition of polyelectrolytes [2, 3] used as spacer. When the desired distance metal-fluorophores is reached, a Rh6G doped layer is deposited.
The study consists in photoluminescence measurements on these structures in order to characterize the effect of the metal on the photoluminescence. We compare these systems with a reference, which is a system with a close geometry except a polystyrene core. The compared photoluminescence signal shows us 3 zones: close and far to the core the PL is quenched, but at a distance around 7 nm the silver core significantly enhance the Rh6G emission. A similar behavior is observed in the total decay rate through lifetime measurements. This demonstrates that core-shell can be used as model systems to analyze the coupling between an emitter and a metallic NP at sub-10 nm distances.
References:
1. Jana K. R. et al, Chem. Mater. 13 2001, 2313-2322
2. Schneider G and Decher G., Nano Letters vol.4, n°10 2004, 1833-1839
3. Schneider G and Decher G., Nano Letters vol.6, n°3 2006, 530-536
9:00 AM - L9.11
High Performance of White Organic Light-Emitting Devices Based on Ultrathin (t-bt)2Ir(acac) Layer
Shengqiang Liu 1 Junsheng Yu 1 Juan Zhao 1 Xu Wang 1
1University of Electronic Science and Technology of China (UESTC) Chengdu China
Show AbstractWe fabricated a series of high performance white organic light-emitting devices (WOLEDs) based on a novel phosphorescent material, bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2&’]iridium (acetylacetonate) [(t-bt)2Ir(acac)], used as yellow emitting layer (EML). The (t-bt)2Ir(acac) emitter with inherently narrow bandgap (2.3 eV) and low triplet energy level (2.2 eV), had outstanding property of trapping and recombining charges to emitting light, which was evidenced from the high photoluminescence (PL) efficiency and high electroluminescent (EL) efficiency of (t-bt)2Ir(acac). One WOLED showed high current efficiency of 79.0 cd/A (at 1550 cd/m2) and power efficiency of 40.5 lm/W (at 1000 cd/m2) with a maximum external quantum efficiency (EQE) of 22.01% by using ultrathin (t-bt)2Ir(acac) layer and doped iridium(III) bis(4&’,6&’-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6) blue EML, which were separated by an interlayer. Similarly, another WOLED using the host-free system of ultrathin (t-bt)2Ir(acac) layer and host-guest doping system of bis[(4,6-difluorophenyl)-pyridinato-N,C2&’](picolinate) iridium (III) (FIrpic) blue EML showed a high current efficiency of 65.3 cd/A and a maximum EQE of 19.04% without any interlayer. The optical and electrical characteristics of these two devices demonstrated efficient energy transfer and proper energy distribution inside the devices. Moreover, we fabricated a stable white emission OLED by combined the three emitting materials, based on the blue and yellow complementary spectrum characteristic. The device performed pure white light emission with the Commissions Internationale de l&’Eclairage (CIE) coordinates varying from (0.29, 0.34) to (0.30, 0.33) while the bias voltage was changed from 6 V to 14 V. The WOLED with triple-phosphor-element EMLs had lower efficiency roll-off, owing to stable recombination zone. The high performance of the three WOLEDs showed the novel (t-bt)2Ir(acac) material was an efficient yellow emission material for white organic light-emitting devices.
9:00 AM - L9.12
Enhancement of Molecular Chiroptical Activity with Plasmonic Nanocubes
Fang Lu 1 Ye Tian 1 Mingzhao Liu 1 Dong Su 1 Hui Zhang 2 Alexander Govorov 2 Oleg Gang 1
1Brookhaven National Laboratory Upton USA2Ohio University Athens USA
Show AbstractChirality is one of the most intriguing structural properties often exhibited by organic and biomolecular constructs. Their chiroptical activity, measured by Circular Dichroism (CD), typically appears in the UV range, and it is broadly used to probe a molecular stereometry. We have discovered that shaped non-chiral plasmonic nanoparticles, namely gold/silver core/shell nanocubes, induce a giant CD signal that is two orders of magnitude stronger for molecules (DNA) attached to the particles than for their free form. The enhanced chiroptical activity presents itself in the plasmonic band of nanoparticles, while a native molecular CD signal in the UV range is unaffected. Based on the experimental and theoretical comparison of nanoparticles of other shapes and materials, we demonstrated a uniqueness of silver nanocube geometry for the CD enhancement. Using the plasmon-induced CD measurements we investigated the changes in DNA configurations due to the environmental factors and hybridization. The discovered phenomenon opens novel opportunities in ultrasensitive probing of chiral molecules and for optical applications based on the chiral nano-elements.
9:00 AM - L9.13
The Direct Correlation of Plasmonic Properties with SERS Enhancement of Stacked Au Nanostructures
Sidney T. Malak 1 Tobias Koenig 1 Zachary A. Combs 1 Rachel Near 2 Mostafa El-Sayed 2 Vladimir V. Tsukruk 1
1Georgia Institute of Technology Atlanta USA2Georgia Institute of Technology Atlanta USA
Show AbstractThe plasmonic response of solid, hollow, and stacked Au nanorectangles (260 nm x 200 nm x 30 nm) with separations of 0-430 nm has been investigated and correlated with their surface-enhanced Raman scattering (SERS) properties to determine how unique structural parameters can be utilized for enhanced sensing. Nanorectangles were fabricated in single and dimer forms using electron beam lithography (EBL) and arranged in an array format to allow for the characterization of specific nanostructures with a variety of techniques. The investigation of individual nanostructures made it possible to determine how their specific geometry (solid, hollow, stacked, slanted stacked) and dimer combinations (bridged, open-open, open-stacked, stacked-stacked) affected their plasmonic and SERS enhancement properties. The isolation of transverse and longitudinal plasmonic modes was achieved through polarized hyperspectral mapping and was corroborated with finite difference time domain electromagnetic modeling. Surface mapping of the nanostructures using Raman spectroscopy was also performed to determine how various structural properties like the stacked or bridged construction affected SERS hot spot formation and the corresponding SERS enhancement. This work provides insight into how unique structural parameters can be employed in EBL nanostructures to tailor their plasmonic properties and to rationally improve SERS sensor design.
9:00 AM - L9.14
Porous Silicon Photoluminescence Modification by Colloidal Gold Nanoparticles
De la Mora Maramp;#237;a Beatriz 2 3 Rocio Nava 1 Rodolfo Zanella 3 Federico Gonzalez 4 Alejandro Reyes-Esqueda 2
1Universidad Nacional Autamp;#243;noma de Mamp;#233;xico Temixco Mexico2Universidad Nacional Autamp;#243;noma de Mamp;#233;xico Mexico Mexico3Universidad Nacional Autamp;#243;noma de Mamp;#233;xico Mexico Mexico4Universidad Autamp;#243;noma Metropolitana Mexico Mexico
Show AbstractMetal nanoparticles on semiconductors are of interest because
of the tunable effect of the surface plasmon resonance on the physical
properties of the semiconductor. Nanoparticles plasmon and dielectric
properties of the semiconductor are considered to have a mayor effect on
the luminescence of these hybrid systems. In this work, colloidal gold
nanoparticles were place on the top of porous silicon single layers. We
show that plasmon effects, refractive index and also surface chemical
modification have effect on the photoluminescence the porous silicon-gold
nanoparticle hybrid system.
9:00 AM - L9.15
Chiral Plasmonic Nanoparticles
Kevin McPeak 1 Christian van Engers 1 Mark Blome 2 3 Jong Hyuk Park 1 Sven Burger 3 2 Yasmina Ries 1 Miguel Angel Gosalvez Ayuso 5 Hui Zhang 4 Alexander Govorov 4 David Norris 1
1ETH Zurich Zurich Switzerland2Zuse Institute Berlin Germany3JCMwave Berlin Germany4Ohio University Athens USA5University of the Basque Country San Sebastian Spain
Show AbstractChiral plasmonic nanoparticles have been predicted to exhibit both strong circular dichroism in the visible spectral range and non-linear optical effects. These properties open up applications in sensing, enantiomer separations, and non-linear optics. Unfortunately, to date the fabrication of colloidal nanoparticles with chiral shape has posed a significant challenge due to a very limited ability to transfer chirality from chiral template molecules to nanoparticles. Here we report a novel route to enantiopure chiral colloidal gold nanoparticles. Importantly, we do not use in principle any chiral molecules or biomolecules and therefore create chiral shapes artificially. Template stripping is applied to anisotropically etched off-cut silicon wafers to prepare nanoparticles with chiral shape of only one handedness. Chiral colloidal suspension of 170 nm gold nanoparticles exhibit an extraordinarily high molar circular dichroism of 5x109 cm-1M-1 and a record high anisotropy factor of 5.5%.
9:00 AM - L9.16
Plasmonic Nanoantenna for Wireless Communications
Abhay Singh 1 Prasoon Meena 1 Shobha Shukla 1 Sumit Saxena 1
1Indian Institute of Technology Bombay Mumbai India
Show AbstractWith the ever increasing need for ultra-fast devices, photonic devices have emerged as a viable option. Although major efforts have been made in designing this transformation, issues like metallic losses and unidirectionality still need to be addressed. In nano-regime, plasmons can efficiently guide and localize electromagnetic waves of visible-near infrared region at metal-dielectric interfaces. Here we report, using Finite Difference Time Domain (FDTD) simulations, a novel design of optical antenna for efficient communication at micro scale. Designed optical antenna emits highly unidirectional radiation as compared to the previously reported designs. Emitter, when excited by strategically placed quantum dot, channels the electromagnetic energy towards the receiver. The device has enhanced power transmission capabilities and better unidirectionality of radiation. This energy was found to be sufficient to excite chromophore and hence, confirm data transfer. This arrangement should be a strong contender for nano optoelectronic devices
9:00 AM - L9.17
Observation of Novel Nanostructures by a Modified Leakage Radiation Microscope
Juan Merlo 1 Fan Ye 1 Michael J. Burns 1 Michael J. Naughton 1
1Boston College Chestnut Hill USA
Show AbstractWe present an experimental study of the optical behavior of novel nanostructures by using a modification of the leakage radiation microscope (LRM) [1]. This technique has demonstrated that it is possible to quantify the near-field interactions between light and nanostructures with a diffraction-limited system. In particular, we observe the resonance modes in a deep circular cavity and the radiation pattern produced by a nanocoaxial structure. We found, in both cases, that the LRM can resolve the characteristic optical features associated with these nanostructures, particularly the plasmonic drumhead modes that was recently reported by our group [2]. Comparison with images obtained by near-field scanning optical microscopy (NSOM) confirms that our results are consistent and show the predicted physical effects. This modified LRM can be used in a wide range of small-scale optical investigations.
[1] A. Drezet, A. Hohenau, D. Koller, A. Stepanov, H. Ditlbacher, B. Steinberger, F.R. Aussenegg, A. Leitner, J.R. Krenn, Mat. Sci. and Eng. B 149, 220 (2008).
[2] F. Ye, M. J. Burns, M. J. Naughton, Nano Lett., 13, 519 (2013).
9:00 AM - L9.18
Enhanced Localized Surface Plasmon Resonance Obtained in Two Step Etched Silicon Nanowires Decorated with Silver Nanoparticles
Emre Mulazimoglu 1 3 Gizem Nogay 2 3 Rasit Turan 2 3 Husnu Emrah Unalan 1 3
1METU Ankara Turkey2METU Ankara Turkey3METU Ankara Turkey
Show AbstractWe have investigated localized surface plasmon resonance (LSPR) of silicon nanowires fabricated by metal assisted etching (MAE) technique. It was found that upon the use of hydrogen peroxide in MAE method degenerates the surface of nanowires and creates oxygen related defect sites. Surface morphology of the nanowires obtained through TEM and optical properties are investigated through PL and diffuse reflectance measurements. The surface characteristics obtained through FTIR. The defect sites obtained upon use of hydrogen peroxide during etching enhance the infrared absorption at higher frequencies and emit visible light by band to band radiative recombinations. Moreoever, almost a 30-fold enhanced LSPR was obtained for 36 nm thick Ag deposited 3 mu;m long Si NWs compared one-step etched Si NWs. This enhancement ratio increases to 100-fold for 24 nm thick Ag deposited samples. This enhancement was attributed to the change in the dielectric constant of effective medium created by defect states at the surface of the nanowires. Furthermore, it was also found that to get an overall enhancement, NW length as well as particle size are the two parameters. Enhancement in LSPR for silver nanoparticle decorated silicon nanowires can be useful for optoelectronic plasmonic devices.
9:00 AM - L9.19
Luminescence in Resonance Fibonacci Arrays of Porous Silicon
Rocio Nava 1 Salvador Escobar 1 Beatriz de la Mora 2 Alejandro Reyes-Esqueda 2
1Universidad Nacional Autamp;#243;noma de Mamp;#233;xico 62580 Temixco Mexico2Universidad Nacional Autamp;#243;noma de Mamp;#233;xico 04510 Mexico Mexico
Show AbstractPhotonic quasicrystal in Fibonacci arrays are structures with
long-range order and interesting properties such as self similar spectra. When
this structures are made of active materials they may give rise to
resonant and strongly coupled when the exciton frequency
coincides with an energy pseudo-gap. In this work we construct 1D
quasiperiodic photonic arrays by the join of two Fibonacci substructures.
Each Fibonacci substructure follows the well-known recursive rule but in
the second substructure dielectric layers A and B are exchanged. These
quasiperiodic arrays gives rise to multiple perfect transmission states. The Fibonacci array are made of luminescence porous silicon. We analyze
experimentally the reflectance and photoluminescence and find a
remarkable increase in the photoluminescence from porous silicon at the
resonance modes.
9:00 AM - L9.20
The Realization of Green-Colored Remote-Type LEDs Combined with E-Sprayed AgIn5S8-ZnS Nanocrystals Film and Dichroic Filters
Ji Hye Oh 1 Su Ji Yang 1 Sung-yeon Jang 1 Young Rag Do 1
1Kookmin University Seoul Republic of Korea
Show AbstractIn this study, green-colored remote-type light-emitting diodes (LEDs) were realized using an AgIn5S8-ZnS nanocrystals (NCs) film sandwiched with short-wavelength pass dichroic filter (SPDF) and long-wavelength pass filter (LPDF). The LPDF, which transmit green wavelength and block blue wavelength, was capped on top of the NCs film to prevent color mixing with blue and green color. The SPDF, which transmit blue wavelength and recycle green wavelength, was located bottom of the NCs film to enhance the green color conversion.
The AgIn5S8-ZnS NCs, which were synthesized by a hot-injection method, were dissolved in a mixed solvent (toluene and dimethylformamide (DMF) with a volume ratio of 2 : 1) and deposited on a glass or SPDF substrate using an electrospray (e-spray) method. The AgIn5S8-ZnS NCs film was solvent annealed with chloroform to enhance the uniformity and transmittance. The LPDF was capped on top of the AgIn5S8-ZnS NCs film and measured with a blue LED. TheAgIn5S8-ZnS NCs and NCs thin films were characterized by photoluminescent (PL), electroluminescent (EL), UV-Vis spectroscopy, X-ray diffraction and atomic force microscopy (AFM).
9:00 AM - L9.21
Magnetooptical YIG and Ce-Doped YIG Film Growth on Slab-Coupled Optical Waveguides
Mehmet Cengiz Onbasli 1 Juan Montoya 2 Steven Spector 2 Gerald F. Dionne 1 Caroline Ross 1
1MIT Cambridge USA2MIT Cambridge USA
Show AbstractRecently, there has been significant interest in integrated optical isolators using magneto-optical (MO) materials, especially those based on yttrium iron garnet (YIG or Y3Fe5O12). Garnets have a mismatch in lattice parameter and thermal expansion coefficient with Si and this hampers the integration of magnetoopticalgarnets into silicon photonic circuits. However, there has been recent progress in integrating garnet films onto various substrates which has facilitated the development of a range of MO opticalisolator designs.
Here, we present pulsed laser deposition of Ce:YIG and YIG films on silicon nitride films and integration of magnetic oxides with optical resonators for obtaining strong magneto-optical response and nonreciprocal wave propagation. The measured Faraday rotation of the Ce:YIG films grown on silicon nitride exceeds 1500 deg/cm at lambda;=1550nm, while bulk Faraday rotation of Ce:YIG is ~4500 deg/cm. Both YIG and Ce:YIG films were measured to have saturation magnetic moment of 135 emu/cm3, rms surface roughness below 3 nm and coercivities between 5 Oe to 50 Oe for different samples. Refractive indices of magneto-optical YIG and Ce:YIG films was 2.19 and optical loss was 40 dB/cm.
While the process parameters developed here strictly apply only to Ce:YIG films grown on silicon nitride, the same process flow with different deposition parameters can be applied to the integration of any crystalline film onto any amorphous substrate that can withstand anneals up to 900°C.
We also present the integration of these oxide films on slab-coupled optical waveguides (SCOW) for inducing non-reciprocal loss or phase shift. Numerical simulations indicate that optical isolation can be achieved with isolation ratio above 20 dB using SCOW integrated with ring resonators. This concept can be applied for optical isolation, circulation, and modulation.
We grew YIG and Ce:YIG on ring resonator-loaded waveguides and measured 2 pm shift in resonance wavelength of the ring resonator for transverse magnetic polarization (TM) when the applied magnetic field was reversed. This shift is in agreement with the expected resonance shift calculated from the measured optical and magnetooptical parameters of the films. This study represents the first report of the theoretical and experimental demonstration of microring coupling into a resonant MO film for optical isolation.
9:00 AM - L9.22
Plasmonic Ag Nanoparticles for Enhancing Thin Silicon Photovoltaics
Richard M. Osgood 1 Stephen Giardini 1 Joel Carlson 1 Michael Ghebrebrhan 1 Peter Stenhouse 1 Richard Kingsborough 2 Vladimir Liberman 2 Mordechai Rothschild 2 Brendan Delacy 3 Steven Kooi 4 Frank Jeffrey 5 Stephen Braymen 5
1US Army NSRDEC Natick USA2MIT Lincoln Laboratory Lexington USA3US Army ECBC Edgewood USA4MIT ISN Cambridge USA5PowerFilm Ames USA
Show AbstractSilicon photovoltaic devices have demonstrated improved power conversion efficiency with the inclusion of plasmonic Ag nano-islands above active layers [1,2]. However, these islands were produced by physically depositing Ag films onto stiff substrates at elevated temperatures, a process probably incompatible with roll-to-roll solar cell manufacturing. We investigate Ag nanoparticles, and their incorporation into thin polymer films, which could more easily be applied to large-area flexible substrates. Strong plasmon resonances have been demonstrated in monolayers of Ag nanoparticles with diameter d < 300 nm, when coated with thin polymer layers having thicknesses < d [3,4] on small batch samples. We study the enhancement of the short-circuit current density (Jsc) and solar spectrum-averaged efficiency in photovoltaic devices having thin (< 1 um) silicon layers. These devices are combined with a monolayer of plasmonic Ag nanoparticles having spherical, core-shell, and “nano-urchin” shapes, and different average inter-particle spacings ranging from less than one radius to several radii. We employ spectrophotometry, a solar simulator, and lasers to characterize the Ag nanoparticle-coated thin silicon films. We measure power conversion efficiency, and interpret it in terms of plasmonically-enhanced enhanced scattering, absorption, and light trapping. We model the effect of Ag nano-urchins, nano-triangles, and core-shell particles on Jsc and the open-circuit voltage, to predict the optimum particles shape, size, and arrangement for maximizing the power conversion efficiency in thin silicon photovoltaic films.
[1] F. Luekermann, et. al., Appl. Phys. Letts. 100 (2012) 253907.
[2] “Plasmon Enhanced Absorption in Photovoltaic Cells”, PhD Thesis of Jeffrey Philip Clarkson, University of Rochester (2010).
[3] M. K. Kinnan and G. Chumanov, J. Phys. Chem. C.114 (2010) 1796.
[4] R. M. Osgood III, et. al., Proc. SPIE 8096, 809610 (2011).
9:00 AM - L9.23
Plasmon Enhanced Phosphorescence Emission of Pure Organic Phosphor Crystals
Dong Hyuk Park 1 Dongwook Lee 2 Jinsang Kim 2 3
1Inha University Incheon Republic of Korea2University of Michigan Ann Arbor USA3University of Michigan Ann Arbor USA
Show AbstractThe hybrid nanostructures of light-emitting materials including metal nanostructures have been intensively studied because of an improvement and control of intrinsic properties through a nanoscale hybrid-junction of two different materials. For example, a promising approach for achieving high luminescence efficiency of light-emitting materials is the use of plasmonic resonance coupling effect by metal nanoparticles (NPs). Extensive researches have attempted to enhance the luminescence efficiency of light-emitting materials using nanoscale metals, through an energy and/or charge transfer effect in a surface plasmon (SP) resonance coupling. The photoluminescence (PL) of light-emitting organic materials incorporated with metal nanostructures can be enhanced when the energy of the SPs in the nanoscale metals matches the energy of the photons emitted by the organic materials. Herein, we introduce the plasmon enhanced phosphorescence emission using pure organic phosphors by incorporation of Ag NPs. We detect a phosphorescent enhancement about 100 times, which is originating from the activating triplet state by incorporation of Ag NPs. The plasmon band of Ag was well-matched with the conduction band of phosphors crystal, which can be generate strongly activate spin-orbit coupling and plasmon energy or charge transfer effect. It is worth note that the pure organic phosphors provide material for the plasmon enhanced phosphorescence.
9:00 AM - L9.24
Novel Blue Fluorescence Emitters Using Dual Core Chromophores
Jongwook Park 1 Beomjin Kim 1 Seungho Kim 1 Hwangyu Shin 1 Jaehyun Lee 1
1Catholic University of Korea Bucheon-si Republic of Korea
Show AbstractWe will show the novel chemical structures based on dual core chromophores for blue emission in OLEDs. One of the derivatives, TP-AP-TP, exhibits a high luminance EQE value of 7.51% and twice the lifetime of a commercialized material, MADN. The dual core chromophore materials have basically narrower PL and EL spectra and better color purity than single core chromophore compounds. Also, it has higher thermal property than the single core chromophore materials. The molecular design and synthesis as well as the device performance of novel organic molecules for highly efficient blue emission will be discussed.
9:00 AM - L9.25
Laser Nano-Structuring of Plasmonic, Stratified Metal/Dielectric Media
Anastasios Siozos 1 Nikolaos Kalfagiannis 2 Demosthenes Koutsogeorgis 2 George Vourlias 3 Wayne Cranton 2 Panos Patsalas 1 3
1University of Ioannina Ioannina Greece2Nottingham Trent University Nottingham United Kingdom3Aristotle University Thessaloniki Greece
Show AbstractPlasmonic materials and devices aim to exploit the unique optical properties of metallic nanostructures to enable routing and manipulation of light at the nanoscale. Lately this field has enabled exciting applications involving chemical and biomedical sensing, information and communication technologies, photovoltaics, lighting, optical encoding and surface decorations. One of the most significant challenges in delivering the aforementioned devices is the material&’s preparation methods in order to produce nanostructures with tunable plasmonic properties. In this work we present a novel engineering approach, namely Laser Annealing (LA), which is capable of subsurface modification of metal 2D structures alternating with dielectrics and meets the requirements of industry, such as fast and large-area processing, spatial selectivity and compatibility with sensitive organic substrates and reel-to-reel production.
We have recently demonstrated the photosensitivity of pulsed laser deposited (PLD) a-AlN doped with Ag nanospheres enabling the reconstruction of both the metal and the dielectric matrix, producing core/shell complexes (consisting of Ag nanoparticles surrounded by a thin layer of w-AlN in an a-AlN matrix) capable of encoding optical information. We further develop this approach by proving the suitability and effectiveness of LA for LSPR manipulation in metal-dielectric stratified media with well-defined sharp interfaces grown by magnetron sputtering; a technique that permits high volume production and is already incorporated in several industrial applications.
Multilayers consisting of alternate layers of AlN (initial layer) and Ag were developed. The bilayer thickness was kept constant at 15 nm and we varied the individual layer thicknesses of Ag and AlN. On top of the repeated structure we applied a cup layer of AlN in all cases, ensuring that the metal phase is not directly exposed to irradiation and ambient contamination, when the samples subjected to LA.
Upon LA and by varying the processing parameters, we delivered Ag nanospheres of various size distribution embedded in a hard, inert and durable ceramic material; suitable for applications under harsh environment. We quantitatively analyze the effects of LA (number of pulses, laser wavelength and fluence) in the processed stratified media not only in a prototype substrate, such as Si wafers, but also in two polymeric substrates: a flexible biaxially oriented polypropylene film (BOPP) and a rigid polycarbonic one. Our findings qualify these metal nanostructure arrays as potential candidates for core nanostructures in plasmonic devices with applications in optical recording/encoding, decorated optical lenses, packaging labeling, among others.
Acknowledgement: Co-funded by the Operational Program "Competitiveness and Entrepreneurship" and the Regional Operational Programs of the Greek National Strategic Reference Framework (NSRF) 2007-2013, Activity "SYNERGASIA II".
9:00 AM - L9.26
Extreme Tunability of Al: ZnO Infrared Plasmonic Multilayers Metamaterial for Telecommunication Applications
Aswini Pradhan 1 K. C. Santiago 1
1Norfolk State University Norfolk USA
Show AbstractMetamaterials can produce new functional devices in which the optical response of a metamaterial can be engineered by manipulating designs and composition, in which their unique optical properties are not seen in individual components. Extreme tunability of metamaterials is limited by materials fabrication. Here we demonstrate the extreme tunability of the crossover wavelength ~0.45 to 0.7 micron in the near-infrared region using both external voltage as well as varying thickness of artificially engineered multilayered gradient films of Al:ZnO fabricated by atomic layer deposition. We anticipate that the multilayer explored here will open up a plethora of applications in the field of nano-plasmonic and metamaterials based devices for telecom and transformative optic applications in the NIR region. We will use several models, including electro-optic effect, and simulation to explain the extreme tunability in this transparent conducting oxides. We believe that the multilayer explored here will open up a plethora of applications in the field of subwavelength scaled electro-optic modulator and metamaterials based devices for telecom and transformative optic applications in the near-infrared region.
Acknowledgments: This work is supported by the DoD (CEAND) Grant Number W911NF-11-1-0209 (US Army Research Office), NSF-CREST (CNBMD) Grant number HRD 1036494.
9:00 AM - L9.27
Time Evolution of Gold Nanodots Deposited on Clean Silicon Substrates during Storage at Room Temperature
Cristina Garozzo 1 Corrado Bongiorno 1 Annamaria Filetti 1 Antonino La Magna 1 Francesca Simone 2 Rosaria A. Puglisi 1
1CNR-IMM Catania Italy2Universitamp;#224; degli Studi di Catania Catania Italy
Show AbstractGold nanodots have received great attention in photovoltaics because they lead to enhanced local electromagnetic field intensity and thus improve the visible light absorption due to plasmonic effects. Moreover, they represent the preferred catalyst for the metal-induced growth of quasi-1D nanostructures, such as nanowires, proposed as novel architectures to improve the cell efficiency. Gold nanodots are usually deposited by sputtering because it is an easy, reproducible and low cost technique. A large quantity of papers present in literature deal with the morphological and structural characteristics of the Au nanodots after the sputtering and their interaction with the substrate, but their time evolution after the deposition during room temperature storage is less known. Our study focuses on the morphological and structural characterization of gold nanodots deposited by sputtering during their time evolution along a period of 14 weeks while stored at room temperature. Au nanodots have been deposited by radio-frequency sputtering on a <100> Si substrate pre-treated to remove the SiO2 native oxide, and have been analyzed by using high resolution TEM. In order to avoid any modification of the material during the preparation for the TEM analysis, the samples have been thinned before the Au sputtering. A large statistical analysis on the distribution in size of the dots has been obtained by digital processing of the TEM images. The results indicated that, after the deposition, a percentage of the deposited gold forms nanodots with high surface density. The remaining part diffuses into the sub-surface regions forming amorphous agglomerates with lateral dimension of a few nanometers. These latter evolve, both in morphology and structure, while the Au nanodots instead preserve their characteristics all over the time. The evolution also involves that the amorphous nanophases undergo to ripening and tend to align to some crystallographic preferential orientations of the substrate.
9:00 AM - L9.28
Mapping the Surface Plasmon Resonances of Single and Double Wall AuAg Nanoboxes via STEM-EELS
Aziz Genc 1 Raul Arenal 2 3 Javier Patarroyo 4 Edgar Gonzalez 5 Victor Puntes 4 6 7 Jordi Arbiol 1 7
1Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC) Bellaterra Spain2ARAID Fondation, 50018 Zaragoza Spain3Instituto de Nanociencia de Aragon (INA), Universidad de Zaragoza, 50018 Zaragoza Spain4Catalan Institute of Nanotechnology (ICN), Campus de la UAB, Edifici Q (ETSE), 08193 Bellaterra Spain5Instituto Geofisico, Facultad de Ingenieramp;#237;a, Pontificia Universidad Javeriana, 110231 Bogota Colombia6Universitat Autamp;#242;noma de Barcelona (UAB), Campus de la UAB, 08193 Bellaterra Spain7Institucio Catalana de Recerca i Estudis Avanamp;#231;ats (ICREA), 08010 Barcelona Spain
Show AbstractIn the last few years, great efforts have been dedicated to study the surface plasmon resonances in metallic nanostructures. This physical phenomenon consists in the collective oscillation of the conduction electrons of a metal excited by an electromagnetic radiation. Plasmonic properties of metal nanoparticles attract great interest owing potential applications in different fields such as electronics, photonics, biotechnology and Raman spectroscopy. The energy of surface plasmon resonances are known to be determined by the size, shape and composition of the nanostructures, therefore it is essential to be able to directly correlate the surface plasmon resonances with the structural properties at the nanoscale. In order to move one step further, we have nanoengineered the morphology of complex metal nanoparticles in order to obtain new plasmonic properties. By means of low loss EELS in an aberration corrected STEM, equipped with a monochromator, we have obtain the in-plane 2D distribution of the plasmonic resonances with sub-eV and sub-nanometer resolutions. The studied complex nanoparticles are different individual AuAg single and double nanoboxes.[1] We have investigated their local plasmonic properties at different parts (corners, edges, etc) and the effects of present voids in their walls. In addition to the mapping of individual nanoboxes, plasmon coupling between different nanoboxes is also studied.
[1] E. González, J. Arbiol, V. F. Puntes, Science, 334, 1377 (2011).
9:00 AM - L9.29
Near-Field Scanning Photocurrent Studies on Graphene Devices
Sameer Grover 1 Ravitej Uppu 2 Arnab Bhattacharya 1 Sushil Mujumdar 2 Mandar Deshmukh 1
1Tata Institute of Fundamental Research Mumbai India2Tata Institute of Fundamental Research Mumbai India
Show AbstractNear-field scanning photocurrent microscopy (SPCM) of graphene and indium arsenide nanowire field effect transistors (FET) with high spatial resolution has been performed. In SPCM, a laser is rastered across the surface of the device and the photocurrent is measured as a function of the laser spot position. Such measurements are extremely useful in studying the mechanisms involved in light-harvesting device such as solar cells and photodetectors and in elucidating fundamental physics of these materials.
The measurements have been performed using a home-made near-field scanning optical microscope constructed by modifying a commercial atomic force microscope. The standard optical detection of cantilever deflection was replaced by a quartz tuning fork based arrangement with an optical fiber tapered to approximately 80 nm acting as the tip. The measurements were done in shear-force mode with the direction of oscillation of the tip parallel to the scanned surface. A closed loop flexural piezoelectric stage was used to scan the sample. This yields a simultaneous map of the photocurrent and the surface topology and the two can be overlaid for comparison.
We estimate the spatial resolution of the photocurrent map to be less than 200 nm, this being one of the key advantages of near field illumination. The resolution is no longer diffraction-limited by the wavelength of light being used. This allows us to explore the photocurrent response of structures with dimensions much smaller than the dimension of the wavelength. We also present far-field SPCM data to contrast the near field measurements and to highlight the improved spatial resolution.
In this study, we perform near-field SPCM on two kinds of devices - graphene and indium arsenide nanowire FETs. Graphene is fabricated by mechanical exfoliation of graphite and indium arsenide nanowires are grown by the vapor-liquid-solid (VLS) growth mechanism. Source and drain contacts are fabricated by conventional electron beam lithography. The variation of the photocurrent with the source-drain and gate voltages has been studied which lets us to investigate the mechanisms responsible for generation of photocurrent such as the photovoltaic and photothermal effect.
Preliminary experiments have already been performed on InAs nanowire devices. The wires resulting from VLS growth mechanism are inherently tapered and one of the key observations from these measurements has been a variation in photocurrent signal along the length of the wire, with a stronger signal in the thicker part of the wire and a weaker signal at the other end.
9:00 AM - L9.30
Optical Properties of ZnO/Silver Nanoparticles for Optically Stimulated Luminescence Radiation Detectors
Eder Jose Guidelli 1 2 Oswaldo Baffa 1 David Clarke 2
1University of Sao Paulo Ribeiramp;#227;o Preto Brazil2Harvard University Cambridge USA
Show AbstractMetal nanoparticles, such as gold and silver, present a fascinating research field due their surface plasmon absorption band, caused by the collective oscillation of the free conducting electrons at nanoparticle surfaces, upon interaction with the electric field of light. These plasmons can interact with surrounding luminescent centers leading to an enhancement of light emission from the centers. In our work we are investigating whether plasmons in noble metal nanoparticles can be used to also enhance the light emission from radiation detector materials based on optically stimulated luminescence (OSL) from radiation-induced defects. This dosimetric technique is largely used for radiation detection and dosimetry in medical procedures such as cancer radiation therapy and radiation protection. Its physical principle is similar to the classical thermoluminescence (TL) process, and is based on the emission of light by a previously irradiated insulator or semiconductor material. However, the stimulation of the irradiated detector occurs upon light exposure instead of heat, as in the case of TL (1). Electrons trapped in the band gap as a result of the ionizing radiation, are then excited by the stimulation light (usually green or blue light), and the relaxation produces emission in the ultra-violet region (2).
In our studies, we have produced ZnO films deposited on glass substrates with previously implanted ZnO seeds, in an aqueous solution containing several concentrations of silver nanoparticles. Zinc oxide has been chosen as an emitter because its band gap is very close to the plasmon resonance of Ag. Furthermore, ZnO by itself has already been shown to be capable of detecting ionizing radiation using several techniques such as OSL, TL and radioluminescence (3). XRD patterns of our nanoparticle films reveals them to be highly oriented but as the concentration of the AgNPs increases, the orientation becomes more random. At the same time, photoluminescence spectra reveals that the increase in the silver nanoparticle concentration decreases the intensity of the green emission band peaked at 630 nm but strongly enhances the near band gap emission band at 385 nm. The enhancement of the UV emission band we have seen makes the ZnO/AgNp films potential candidates for application in optically stimulated luminescence dosimetry. These and other properties, including microstructures and other optical properties, of these materials will be described.
1. Yukihara EG, McKeever SWS. Optically stimulated luminescence (OSL) dosimetry in medicine. Physics in Medicine and Biology 2008;53:R351-R379.
2. Eduardo G. Yukihara, McKeever SWS. Optically Stimulated Luminescence: Fundamentals and Applications. 1st ed: John Wiley & Sons Ltd; 2011.
3. Gorokhova EI, Anan'eva GV, Demidenko VA, et al. Optical, luminescence, and scintillation properties of ZnO and ZnO:Ga ceramics. Journal of Optical Technology 2008;75:741-746.
9:00 AM - L9.32
Manipulation of Optical Properties of Eu3+ Complex with Plasmonics
Rabia Hussain 1 Natalia Noginova 1
1Norfolk State University Norfolk USA
Show AbstractHighly luminescent metal-organic complexes of Eu3+ ions are finding applications in many fields of science including biotechnology and medicine. We explore a possibility of engineering optical properties of such complexes at nanoscale, by coupling them to plasmonic elements. Strong effects of coupling are observed in emission spectra, polarization and radiation patterns. Significant modification of absorption spectra in vicinity of silver is demonstrated as well. Experimental findings are compared with numerical simulations.
9:00 AM - L9.33
Self-Assembled Plasmonic Nanoring Cavity Arrays for SERS and LSPR Biosensing
Hyungsoon Im 1 2 Kyle C Bantz 3 Si-Hoon Lee 1 Timothy W Johnson 1 Christy L Haynes 3 Sang-Hyun Oh 1
1University of Minnesota Minneapolis USA2Massachusetts General Hospital Boston USA3University of Minnesota Minneapolis USA
Show AbstractSurface-enhanced Raman scattering (SERS) and localized surface plasmon resonance (LSPR) spectroscopy have emerged as viable analytical tools for the detection of analytes. It has been suggested that large SERS enhancements are achieved when the analyte of interest is placed near a noble metal gap or crevice feature. However, the lack of reproducible high-throughput fabrication techniques with nanometric control over the gap size has limited practical applications. Here, we report a novel method for inexpensive, high-throughput fabrication of a periodic array of ring-shaped nanocavities with 10 nm gap size by combining nanosphere lithography with straightforward batch processing steps, namely, atomic layer deposition (ALD) and ion milling. Using the batch fabrication techniques, we have produced the nanogap structures in cm2-sized areas with the nanogap dimension below 10 nm. In the resulting hybrid nanostructure, incident light resonantly excites ring-shaped 10-nm-gap cavities formed alongside the curvature of Ag nanospheres. The resonant coupling between the Ag nanospheres and the ring-shaped nanocavity boosts light-coupling efficiency into the ultra-thin gap. Compared to conventional Ag films on nanosphere (AgFON) substrates, the addition of nanoring cavities improves the SERS enhancement factor by at least an order of magnitude, and the resonance wavelength can be readily tuned by changing the size of nanospheres used. After optical characterization of the nanoring cavity substrates, we also employ the nanogap structures for the detection of adenine, a commonly detected molecule in intrinsic DNA sensing experiments, and demonstrate improved detection limits as well as the use of the same substrate for concurrent LSPR biosensing. Considering the reproducibility, high-throughput fabrication, and high SERS enhancement factor, the developed method will have significant implications for the practical application of engineered SERS substrates.
9:00 AM - L9.34
Inter-Dot Distance Dependence of Photoluminescence of Au25 Nanoclusters
Mitsuru Inada 1 Kousuke Takahashi 1 Hideya Kawasaki 2 Tadashi Saitoh 1
1Kansai University Osaka Japan2Kansai University Osaka Japan
Show AbstractMetal nanocluster (NC) have some attractive behaviors such as size dependent fluorescence, superparamagnetic properties and nonlinear carrier transport. Recently, highly fluorescent Au NCs are reported, which are important to applicant for biosensors, imaging labels and optoelectronic devices. Optical coupling between NCs is considered to be importance both fundamentally and technologically. In this study, we investigate the inter-dot distance dependence of photoluminescence (PL) of human serum albumin protected Au25 (HSA-Au25) NCs. We measured PL spectra of HSA-Au25 NCs varying inter-dot distance. The inter-dot distance controlled by changing the density of NCs in water solvent. We observed strong luminescence of HSA-Au25 at 1.9 eV with small swell at 1.7 eV. Photoluminescence excitation (PLE) spectra revealed that absorption band of 1.9 eV emission was at around 2.5 and 3.5 eV. With reduction of the inter-dot distance, the PL intensity was decreased and the peak position was slightly red-shifted. On the condition, the intensity of higher absorption band at 3.5 eV of PLE spectrum was relatively decreased. This shows that non-radiative transition probability of higher absorption band increased with decreasing inter-dot distance. The reason of this is not yet cleared, but one possible reason is energy or charge transfer to non-radiative intermediate state of adjacent Au25 NCs. The results indicate that inter-dot distance plays an important role in the luminescent properties of HSA-Au25 NCs.
9:00 AM - L9.35
Highly Responsive In2Se3 Nanosheet Based Photodetector
Robin Jacobs-Gedrim 1 Mariyappan Shanmugam 1 Nikhil Jain 1 Christopher Durcan 1 Thomas Murray 1 Richard Matyi 1 Richard Moore 1 Bin Yu 1
1State University of New York at Albany Albany USA
Show AbstractWe demonstrated a highly responsive photodetector based on novel two-dimensional In2Se3 nanosheets. Few-layer nanosheets of alpha-phase Indium(III) Selenide (α-In2Se3) are prepared by micromechanical exfoliation. The derived nanosheets are shown to be of single phase, highly crystalline, and nearly stoichiometric with low-level selenium defect density. Nanosheets with sub-ten-layer thickness were prepared and used to fabricate a photodetector device with intriguing properties. When operated in the photoresistor functional mode the In2Se3 nanosheet photodetector exhibits a response time of 1.8x10^-2 seconds, a responsivity of 1.04x103 A/W in the UV spectral region (400 nm wavelength) under 5 V bias, and a corresponding External Quantum Efficiency greater than 8.9x10^4 % with specific detectivity on the order of 9.4x10^12 Jones. The response of photodetector extended into visible and near-infrared spectral range. The exceptional optoelectronic responsivity of the In2Se3 nanosheet (with reference to its bulk counterpart) could be attributed to largely increased carrier lifetime and nano-size effects in the highly crystalline 2D material system. The results point to the potential pathway towards 2D semiconductor-based light sensors capable of real time imaging and detection in low-light conditions.
9:00 AM - L9.36
Improved Light Harvesting Effects of Dye-Sensitized Solar Cells Containing Tailor-Designed Hybrid Nanostructures
Yoon Hee Jang 1 Yu Jin Jang 1 Li Na Quan 1 Jihyeon Kim 1 Dong Ha Kim 1
1Ewha Womans University Seoul Republic of Korea
Show AbstractDye-sensitized solar cells (DSSCs), which are one of the most potential photovoltaic devices, have attracted considerable attention as an alternative platform to the future renewable energy production owing to their high solar energy conversion efficiency as well as relatively low fabrication cost and simple process. The photon management is a crucial factor in solar cells to enhance the light absorption and thus their performance. In order to increase the capability of light harvesting, diverse efforts have been devoted by many research groups. Recently, photonic elements such as 1-dimmentional Bragg stacks and 3-dimmentional inverse opal structures are successfully introduced into photoelectrode to absorb the non-absorbed photons by light active materials. Another promising strategy to improve the light trapping effect can be coupling of surface plasmon resonance (SPR) effects of metallic nanostructures, which will lead to further enhancement of the photocurrent. Localized SPR (LSPR) phenomenon, collective oscillations of electrons in metallic nanostructures, is induced by excitation of hot-electrons that can lead to the optical field enhancement at the resonance wavelength. LSPR has very high sensitivity that is influenced by the size and shape of nanoparticles as well as the index of surrounding environment.
In this work, we introduce functional tailored hybrid nanostructures into the TiO2 nanoparticles based DSSCs to improve the light harvesting of dye molecules and thus the performance of the cells. First, periodic organic-inorganic multilayer films are constructed by stepwise buildup of block copolymer (BCP) inverse micelles and included in the counter electrode as light reflecting layers. The multilayered BCP films exhibit strong reflective color and well-defined photonic stop bands. The layered films are integrated into the non-conducting side of counter electrodes and thereby remarkably enhanced overall power conversion efficiency is achieved, which can be attributed to the increased light harvesting by sensitized dye molecules. Second, plasmonic DSSCs containing tailor-designed Au-TiO2 core-shell nanostructures with unique LSPR property are demonstrated and improved performance is achieved. Enhancement in efficiency can be attributed to not only the increase of the dye excitation by LSPR effects associated with near-filed enhancement and scattering but also generation of additional photocurrent induced by direct hot-electron transfer from plasmonic core-shell structures to TiO2 conduction bands. The simple yet novel approaches presented in this work can be utilized as a generalized protocol and applied to other energy conversion devices to improve the device capability.
9:00 AM - L9.37
ITO-Free Organic Light-Emitting Diodes by Using Self-Organized Polymeric Anodes with Surface Plasmon Resonance Effect
Su-Hun Jeong 1 Seong-Hoon Woo 1 Tae-Hee Han 1 Min-Ho Park 1 Tae-Woo Lee 1
1Pohang University of Science and Technology (POSTECH) Pohang Republic of Korea
Show AbstractTo set up a true ubiquitous environment, the optoelectronic devices, such as solar cell, touch screens, and displays, should be not only be portable; they must be able to change their shapes freely. In other word, these optoelectronic devices should be flexible. In order to embody fully flexible optoelectronic devices, conventional transparent anode materials represented by indium-tin oxide (ITO) should be replaced with any other flexible anode materials due to its brittleness. Furthermore, the increasing price due to scarcity of indium makes it difficult for its use in low-cost, large-area optoelectronics. Here, we embody ITO-free organic light-emitting diodes (OLEDs) using self-organized conducting polymers as transparent anodes without any hole injection layer (HIL). The self-organized conducting polymers are prepared based on poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) in which 5wt% DMSO is added to enhance their conductivity. As a key component, perfluorinated polymer (PFI) is included to achieve a high work function and hydrophobicity by inducing surface-enriched PFI layer. They show excellent tuning of work-function. The maximum work-function of the anode is 5.8 eV which is the highest value among the flexible anodes which have been reported until now. Moreover, transparency is higher than 90 % in all the visible range. Also, additional silver nanoparticle layer under our polymeric anode makes it possible to utilize the surface plasmon resonance effect. Our OLED devices based on our polymeric anodes with silver nanoparticles showed highly improved current efficiency and stability even with a simplified structure compared to conventional ITO/HIL devices. Even the stability of OLEDs based on our polymeric anodes was improved. Furthermore, we analyzed hole-injection characteristics between the modified polymeric anode layer and a hole-transport layer using dark injection space-charge limited current (DI-SCLC) measurement. We concluded that the improved properties of our polymeric anode based devices come from highly efficient hole injection and surface plasmon resonance effect.
9:00 AM - L9.38
Electromagnetic Interaction between a Laser Beam and Semiconductor Nanowires Deposited in Different Substrates: Raman Enhancement in Si and SiGe Nanowires
Julian Anaya 1 Juan Jimenez 1 Andres Rodriguez 2 Tomas Rodriguez 2
1Universidad de Valladolid Valladolid Spain2Universidad Politamp;#233;cnica de Madrid Madrid Spain
Show AbstractRaman scattering in Si and SiGe nanowires (NWs) presents antenna effects strongly dependent on the electromagnetic coupling of the system laser/NW/substrate. The antenna effect of the Raman signal was measured in individual NWs deposited on either Al or Ge substrates, and also in air. The one phonon Raman band intensity in NWs, either Si or SiGe, can reach high values depending on the system configuration; values of Raman intensity per unit volume more than a few hundred times with respect to bulk Si were observed. The Raman intensity measured depends on the light polarization with respect to the NWs axis. The complex refractive index of the substrate plays a major role in the Raman enhancement, which was also observed to depend on the laser wavelength. The Raman intensity is determined by the electric field inside the NW; because of the sub-wavelength dimension of the NW diameter, the distribution and intensity of the electric field in the NW presents a marked dependence with the diameter. It adopts different distributions according to the dimensions, the wavelength and the surrounding media. Local spots of the electric field are observed inside the NW.
We present herein the calculation of the electric field in the NWs using finite element analysis (FEM) for different substrates. The theoretical solutions are illustrated with the experimental Raman spectra of individual Si and SiGe NWs. The results are discussed in terms of the electromagnetic interaction between the laser beam, the NWs and the substrate.
9:00 AM - L9.39
Effect of Annealing Temperatures of Sol-Gel Based Ga-Doped ZnO Electron Transport Layer on Quantum Dot Light-Emitting Diodes
Heeyoung Jung 1 Myeongjin Park 1 Thambidurai Mariyappan 1 Jaehoon Lim 1 Jeonghun Kwak 2 Kookheon Char 3 Seonghoon Lee 4 Changhee Lee 1
1Seoul National University Seoul Republic of Korea2Dong-A University Busan Republic of Korea3Seoul National University Seoul Republic of Korea4Seoul National University Seoul Republic of Korea
Show AbstractWe studied the effect of annealing temperatures of gallium (Ga)-doped zinc oxide (ZnO) electron transport layer (ETL) on the electrical and optical properties of inverted quantum dot (QD) light-emitting diodes (QLEDs) with red-emitting CdS@CdZnS QDs. Metal oxide nanoparticles, recently, have been used as the ETL of QLEDs because of their superior processibility, electrical and optical properties. However, their electron mobility is limited up to 10-3 cm2/Vs. To increase the electron transporting ability, we adopted Ga-doped ZnO films deposited by sol-gel based spin-coating process as the ETL of QLEDs, and investigated the performances of QLEDs with different annealing temperatures from 150°C to 350°C. When the Ga-doped ZnO layer was annealed at 350°C, QLEDs showed the best performance in terms of low turn-on voltage and high external quantum efficiency of 5%. We found that the device performance was affected by the morphology changes of Ga-ZnO films as the annealing temperature was varied. The AFM analysis indicated that higher annealing temperature resulted in larger grain size of Ga-doped ZnO films while lower annealing temperature leaded to smaller grain size. The electron mobility of Ga-doped ZnO film with larger grains is higher than that with smaller grains since carriers are scattered at grain boundaries.
9:00 AM - L9.40
Large Area Gold Nanoparticle Based Optical Absorbers
Shideh Kabiri 1 Pramod Kumar Singh 1 Sameer R Sonkusale 1
1Tufts University Medford USA
Show AbstractGold nanoparticles can be utilized as plasmonic elements in making of an absorber from near infrared to visible region. Such absorbers have a lot of applications in photovoltaics and imaging. In this work we present a large area fabrication of gold nanoparticles based absorber using a thermal method on quartz and silicon substrates.
To make the gold nanoparticles, a thin layer of gold was deposited on the substrate (1.5 cm×1.5 cm) using DC sputtering then samples were annealed in the nitrogen ambient for 30 minutes at different temperature between 300, 550 and 750 °C. Gold nanoparticles are formed on substrate after annealing. Samples was fabricated with annealing gold layers with different thickness of 6 nm, 9 nm and 14 nm. The morphology of nanoparticles was studied using scanning electron microscopy (SEM). According to our result, the size of nanoparticles is dependent on the thickness of the gold seed layer prior to annealing, and the shape is dependent on the annealing time and temperature. In the next step nanoparticles are coated with the 130 nm of indium tin oxide (ITO) followed with deposition of 200 nm of silver layer as the back metal. The reflection light was measured using a UV-Vis reflectometer in the range of 400-800 nm wavelengths. Our results shows more than 70% decrease in the reflection at the resonance frequency (540, 580 and 670 nm) and between 40-60% decreases at all over the wavelength band. Absorber was also simulated using CST microwave studio software and simulation shows strong agreement with measurement results.
9:00 AM - L9.41
Close-Packed Plasmonic Au Nanoparticle Arrays on Core-Shell Type Polymer Particles
Masaaki Kanahara 1 Masatsugu Shimomura 1 Hiroshi Yabu 1 2
1Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University Sendai Japan2Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) Kawaguchi Japan
Show AbstractAu nanoparticles (NPs) coated composite microspheres have received considerable attention due to various applications in the fields of electronics, photonics, and biotechnology. Owing to the localized surface plasmon resonance (LSPR), Au NPs exhibit unique optical and electronic properties. Since these features can be tuned by controlling their sizes, shapes, and interparticle distances, the arrangement of Au NPs on the microsphere is one of the important factors to realize their unique properties. By fabricating close-packed Au NPs arrays on microsphere that have high surface-to-volume ratio and dispersibility in various solvents, such composites can be used in various applications, such as surface enhanced Raman scattering (SERS), medical imaging, photothermal therapy, and drug delivery. However, it remains difficulties to fabricate close-packed Au NPs arrays on the microspheres. In this study, we successfully fabricated close-packed Au NPs arrays with nanoscale gaps on polymer particles by simple mixing of pre-formed polymer particles and Au NPs via electrostatic interactions.
Aqueous dispersion of submicron-sized core-shell type polymer particles comprised of polystyrene (PS) cores and amino-terminated poly (butadiene) (PB-NH2) shells was prepared by evaporating tetrahydrofuran from a polymer solution containing PS, PB-NH2, and water. Since the surfaces of the polymer particles were composed of ionized PB-NH3+, the polymer particles had positive surface charges. When the aqueous dispersions of the polymer particles and negatively charged citrate-stabilized Au NPs with a diameter of 20 nm were mixed at room temperature, the Au NPs adsorbed to the polymer particles via electrostatic interactions. Transmission electron microscope (TEM) observation revealed that the Au NPs were incorporated into the PB-NH2 shell. Since the PB-NH2 has a lower glass transition temperature (Tg) than room temperature, the PB-NH2 shell has low viscosity. When Au NPs were adsorbed onto the surface of the core-shell particles, positively charged PB-NH2 chains attached to the negatively charged Au NPs to form ion pairs by electrostatic interactions. The adsorbed PB-NH2 chains formed core-shell like polymer blush structures around the Au NPs, as a result, Au NPs were encapsulated into the PB-NH2 matrix. When the shell thickness of the core-shell particle was compatible with the diameter of Au NPs, highly ordered Au NPs arrays were formed at the shells. Scanning electron microscope (SEM) and transmission electron microtomography (TEMT) observations revealed that close-packed Au NPs arrays with about 5 nm interparticle spacings were formed at the PB-NH2 shells of the core-shell type polymer particles. From the ultraviolet-visible absorption (UV-Vis) measurement, the fabricated composite particles exhibited a broad absorption band in 600~700 nm regions due to the plasmon coupling among adjacent Au NPs.
9:00 AM - L9.42
Monte-Carlo-Based Electromagnetic Modeling: Accounting for Inhomogeneous Broadening in Polydisperse Ensembles of Photonic and Plasmonic Elements
Mikhail A Kats 1 Herman Gudjonson 1 Kun Liu 2 Zhihong Nie 3 Eugenia Kumacheva 2 Federico Capasso 1
1Harvard University Cambridge USA2University of Toronto Toronto Canada3University of Maryland College Park USA
Show AbstractMany experimental systems consist of large ensembles of uncoupled or weakly interacting elements operating as a single whole; this is the case in many experimental systems in nano-optics and plasmonics including colloidal solutions, plasmonic nanoparticles, dielectric resonators, antenna arrays, and others. In such experiments, measurements of the optical spectra of ensembles will differ from measurements of the independent elements even if these elements are designed to be identical as a result of small variations from element to element, known as polydispersity. In particular, sharp spectral features arising from narrow-band resonances will tend to appear broader and in extreme cases can be washed out completely. Here, we explore this effect of inhomogeneous broadening as it occurs in colloidal nano-polymers comprising self-assembled nanorod chains in solution. Using a technique combining finite-difference time-domain (FDTD) simulations and Monte-Carlo sampling, we predict the inhomogeneously-broadened optical spectra of these colloidal nano-polymers, and observe significant qualitative differences compared to the unbroadened specta. The approach combining an electromagnetic simulation technique with Monte-Carlo sampling is widely applicable for quantifying the effects of inhomogeneous broadening in a variety of physical systems, including those with many degrees of freedom which are otherwise computationally intractable.
9:00 AM - L9.43
Hybrid Core Shell Plasmonic Nanostructures
Akram A Khosroabadi 1 Palash Gangopadhyay 1 Robert A Norwood 1
1University of Arizona Tucson USA
Show AbstractInterests in patterned polymer based nanodevices and sub-100 nm metal and transparent conducting nanostructured electrodes have led us to modify the traditional imprint lithography technique to enable fabrication of an array of sub-100 nm diameter electrode structures [1]. In this approach, an e-beam lithographed hard Si or SiC master is used to directly imprint a large area nanopattern onto polyacrylonitrile (PAN) film. The PAN film is then cured at ~ 200 °C to synthesize nanostructures. Metal and metal oxides can be coated with different thickness onto the PAN structures to create nanostructured electrodes. ITO nanostructured electrodes with nanopillars of 170 ± 8.8 nm diameter and 442 ± 10.6 nm high [2] encompassing a 1 cm × 1 cm area were fabricated. E-beam deposition of ITO resulted in thinner (up to 15 nm) sidewalls and a thicker coating on the top and bottom of the pillars. A thin layer of Ag at the center of ITO layer was deposited to increase sample conductivity, resulting in a multilayer sample with 70 nm ITO on the bottom, followed by 10 nm Ag and then 70 nm ITO on top. By optimizing the thickness of each of these layers one may optimize the trade-off between conductivity and transparency of the sample. The addition of the Ag also leads to localized and tunable surface plasmon resonances. At plasmon resonance the reflection of sample is minimized and absorption in the sample will dominate [3]. Experimental and simulated reflection spectra of this structure are in good agreement, including the appearance of sharp spectral features that are absent in a simple planar analog. The simulated Brewster angle of the nanopillars decreases compared to the planar reference sample by up to 10-13 degrees depending on the height of the pillars and appears to an indication of a reduced refractive index. The depolarization factor that was obtained by ellipsometry is about 0.05 and as expected from the ellipsoidal shape of the pillars [4].
References:
[1] J. Thomas et. al., “Nanoimprinting by melt processing: An easy technique to fabricate versatile nanostructures”, Advanced Materials 23, 4782-4787 (2011).
[2] A. A. Khosroabadi et. al., “Fabrication, electrical and optical properties of silver, indium tin oxide (ITO), and indium zinc oxide (IZO) nanostructure arrays” Phys. Status Solidi A, 210: 831-838. doi: 10.1002/pssa.201329129
[3] A. A. Khosroabadi et. al., “Hybrid Nanostructured plasmonic Core-Shell Electrodes”, manuscript under preparation.
[4] A. A. Khosroabadi et. al., “Spectroscopic ellipsometry on metal and metal oxide multi-layer hybrid plasmonic nanostructures”, manuscript under preparation.
9:00 AM - L9.44
Highly Efficient Inverted Polymer Light-Emitting Diodes with Polyethylene Imine Electron Injection Interlayer
Young-Hoon Kim 1 Tae-Hee Han 1 Chang-Lyoul Lee 2 Tae-Woo Lee 1
1POSTECH Pohang Republic of Korea2GIST Gwangju Republic of Korea
Show AbstractInverted polymer light-emitting diodes (IPLEDs) has been expected as a flexible display due to easy to fabrication, low process cost, large area application and possible roll-to-roll process. However, the air-sensitivity of Cs2CO3, electron injection interlayer (IL), limits their feasibility as a flexible devices and diffused Cs+1 ions reduce efficiency by inducing exciton quenching site in emitting layer. In order to solve these problems, we studied two air stable polymer interlayers (ILs), branched polyethyleneimine (PEI) and polyethyleneimine ethoxylated (PEIE), which can increase electron injection into emitting polymer more than Cs2CO3 by forming strong interface dipole. We also studied the effect of [N+]/[C] ratio of two polymer ILs on work function change of underlying ZnO by X-ray photoelectron spectroscopy (XPS). We can find that, with polymer ILs thickness, work function of underlying ZnO tends to increase by ultraviolet photoelectron spectroscopy (UPS) and exciton quenching tends to decrease by photoluminescence (PL). Finally, in IPLEDs with optimum ILs thickness, 8-nm PEI, we achieved high current efficiency (12 cd A-1) and power efficiency (4.5l m W-1) that were quiet higher than those with Cs2CO3 (8cd A-1 and 1.9lm W-1). The impedance spectroscopy is also used to study the roll of polymer ILs which block hole injection into ZnO in low bias and facilitate electron injection into emitting layer in high bias.
9:00 AM - L9.45
Fabrication of Metal Nanowires by Mechanical Deformation Using Anodic Porous Alumina and Its SERS Property
Toshiaki Kondo 1 Takashi Yanagishita 1 Kazuyuki Nishio 1 Hideki Masuda 1
1Tokyo Metropolitan University Hachioji Japan
Show AbstractFabrication processes of metal nanostructure arrays have attracted increasing attention because of its applicability of enhanced electric field of incident light based on localized surface plasmon resonance (LSPR) [1,2]. Metal nanowire is one of the candidates to enhance electric field of the light. In addition, the nanowires have large surface area. Various types of applications based on nanowires, such as photovoltaic cells, nonlinear optics and sensing devices, have been proposed. Precise control of geometrical structures of the nanowires is important because the properties of LSPR are substantially dependent on the shape and arrangement of the nanowires. However, processes to fabricate the array of the geometrically controlled metal nanowires have not been established. In the present work, we studied the fabrication of metal nanowires by mechanical deformation process using anodic porous alumina, and its application to a substrate for the surface-enhanced Raman scattering (SERS) measurement. One of the advantageous points of using the anodic porous alumina to fabricate nanostructures is that the shape and arrangement of the nanostructures can easily be controlled by changing the geometrical structures of the porous alumina. Electrodeposition process using anodic porous alumina as a template is usually used to fabricate the metal nanowires. There are several metals that have difficulties to electrodeposit. Al nanowire is attracted attention due to the properties of LSPR. However, it is difficult to fabricate the Al nanowires because of its difficulties of the electrodeposition. By the present process based on mechanical deformation, it becomes easy to fabricate the nanowires composed of various metals including Al.
Anodic porous alumina was fabricated by anodizing Al in acidic solution. The porous alumina was pressed onto a surface of the metal (Au, Ag, Al etc.) by using an oil press. The metal was mechanically deformed, then, filled each nanohole of the porous alumina. After removing the alumina, the metal nanowires were obtained. The diameter and length of the nanowires were precisely controlled by changing the geometrical structures of the porous alumina. The metal nanowire arrays were applied to the substrate for the SERS measurements. SERS spectra were measured using a Raman microscope (excitation wavelength: 633 nm). The obtained structure was dipped in a pyridine solution and dried in air before the measurement. The SERS peaks originating from the adsorbed pyridine molecules were observed at 1014 and 1040 cm-1. The intensity was strongly dependent on the geometrical structures of the nanowires. It is expected that the present process can be applied to fabricate functional optical devices, solar cell, chemical and biological sensing devices.
[1] T. Kondo, H. Masuda, K. Nishio, J. Phys. Chem. C, 117, 2531 (2013).
[2] T. Kondo, H. Miyazaki, K. Nishio, H. Masuda, J. Photochem. Photobiol. A, 221, 199 (2011).
9:00 AM - L9.46
HiPIMS Reactive Deposition on TiO2 - Effect of Shutter Opening on Pulse Shape and Deposition Rate
Anna Kossoy 1 Seyedmohammad Shayestehaminzadeh 1 Rogvaldur L Magnusson 1 Tryggvi K Tryggvason 1 Haflidi Gislason 1 Kristjan Leosson 1 Sveinn Olafsson 1
1Science Institute-University of Iceland Reykjavik Iceland
Show AbstractDeposition of TiO2 by reactive High Power Impulse Magnetron Sputtering (HiPIMS) was extensively researched during last years in terms of factors that influence film morphology as well as in terms of factors that affect state of plasma and thus pulse shape and deposition process and remarkable results were reported recently. HiPIMS as-grown polycrystalline TiO2 films (rutile phase) have quality far superior to as-grown by DC magnetron sputtering in terms of roughness, phase homogeneity, refractive index and microstructure, and perform exceptionally as a part of high contrast Bragg mirrors, where it was demonstrated that transmission through metal film can be substantially enhanced by resonant plasmon tunneling making those heterostructures promising as transparent contacts for light-emitting devices. The major difference of HiPIMS from DC magnetron sputtering is the high energy density that is delivered to the growing film by the high voltage pulses at a certain repetition frequency. Since HiPIMS is relatively new modification of DC magnetron sputtering there is an ongoing research activity attempting to determine the factors that affect the plasma and deposition process in order to optimize its performance and efficiency. The shape of the pulse current contains a lot of information on the physics of deposition process and its dependence upon energy density, strength of magnetic field and factors that alter target oxidation was reported.
In this work we describe the effect that shutter state (open/close) has on target oxidation, and the pulse waveform during reactive deposition of TiO2. This results in time dependent behavior of the deposition rate. TiO2 films were grown by reactive HiPIMS in Ar/O2 gas mixture at 500 C from metallic Ti target. The growth was studied during initial 10 min after shutter was opened, after the target was pre-sputtered for a long period with the shutter closed. With shutter opened the pulse current shape and process energy changed. The deposition rate which was high initially, 0.15 nm/sec, dropped to 0.115 nm/sec (>23 %) during the first 2 minutes and continued to decrease for the remaining 10 minutes of deposition. Film thickness and growth rate were determined from X-ray reflectivity. Simultaneously the integrated energy involved in deposition process was monitored. Film thickness was found to have a linear relation on the integrated deposition energy. Thus for materials where deposition rate instability is observed it is possible to calibrate and control the film thickness by monitoring the integrated pulse energy and end growth when the desired integrated pulse energy level has been reached.
9:00 AM - L9.47
Patterning of Plasmonic Nanomaterials by Energetic-Assisted Scanning Thermal Lithography
Chun-Min Huang 1 Yu-Chen Huang 1 Chung-Hsien Yeh 1 Changshu Kuo 1
1National Cheng Kung University Tainan Taiwan
Show AbstractScanning thermal lithography (SThL) was demonstrated with the addition of energetic peroxides for synthesis and patterning of silver nanoparticles in polymer films. SThL samples were prepared by spin-coating poly(ethylene terephthalate) (PET) thin films preloaded with silver nitrate precursors and energetic peroxides, cumene hydroperoxide (CHP). Localized thermal analysis of these samples indicated the energetic peroxide decomposed at the temperature as low as 80 C. Above these temperatures, SThL thermal probe initiated the peroxide decomposition, which caused the localized discharge of exothermal energy close to the SThL thermal probe. This additional energy effectively compensated the joule shortage and the rapid cooling in the thin film samples. As a result, SThL fabrications can be operated at the relatively lower temperature, and the extra and localized joule energy significantly enhanced the chemical synthesis of silver nanoparticles, which were SThL-patterned and embedded in the polymer thin films. Polymer thin films were carefully characterized in terms of the dispersion of the energetic peroxide and silver precursor prior to the SThL process. After the SThL patterning, surface plasmon resonance (SPR) scattering of these silver nanoparticles were observed by the dark-field optical microscopy, as well as the transmission electron microscopy. Variations in the peroxide concentrations, SThL temperatures, and SPR signatures were investigated.
9:00 AM - L9.48
Effect of Photonic Crystal on Transparent Nanocrystalline Glass-Ceramic Scintillator for X-Ray Imaging
Gyu Hyon Lee 1 Yaru Ni 1 Brent Wagner 2 Christopher Summers 1 Zhitao Kang 1 2
1Georgia Institute of Technology Atlanta USA2Georgia Tech Research Institute Atlanta USA
Show AbstractThe phosphor screens used in current x-ray detectors are micron-sized powder phosphors and the spatial resolution is limited due to strong light scattering. The resolution limit restricts the usefulness of x-ray in various medical applications. Transparent scintillator screens can produce higher spatial resolution and have the potential to significantly enhance current medical and biological imaging techniques if the efficiency is improved. A photonic crystal layer on the surface of the scintillator can improve the light output efficiency. It can enable the extraction of photons which would otherwise be reflected within the scintillator due to total internal reflection.
In this study, we investigate the use of a photonic crystal layer on transparent nanocrystalline scintillators. The nanophosphors, terbium doped gadolinium fluoride nanoparticles, are embedded in an aluminosilicate glass-ceramic matrix. The scintillators were prepared by a melt-quench method followed by annealing. The gadolinium fluoride nanophosphors were precipitated within the glass-ceramic matrix during this process. The photonic crystal pattern was directly created on the top layer of scintillators material by electron beam lithography followed by reactive ion etching. The photonic crystal pattern and the scintillators were physically characterized by scanning electron microscopy, atomic force microscopy and transmission electron microscopy. Their luminescence and scintillation properties such as photoluminescence, photoluminescence excitation, reflectance and transmission were examined and compared with scintillators without the photonic crystal layer.
9:00 AM - L9.49
Ultra-Low-Reflective and Self-Cleaning Surfaces
Heon Ju Lee 1 Eusun Yu 1 Myoung-Woon Moon 1
1KIST Seoul Republic of Korea
Show AbstractUltra-low-reflective and super-hydrophobic surfaces are required for solar cells, large outdoor display panels, and large road signs to increase their performance and durability through self-cleaning in harsh environments.
It has been developed for well designed and micro/nano fabricated surface which has reflectance of less than 1-2 % in visible resign. However, it was still challenge to provide the solution for large area with low-cost and uniform properties. Here, we have developed a novel method to fabricate ultra-low reflective surfaces on Si with hierarchical nano-structures by the combination of Si and AlOOH (boehmite) nano-structures.
Using CF4 plasma etching, Si surfaces were nano-structured with pillar-like structures by selective etching with self-masking by fluorocarbon residues. AlOOH nano-flakes were formed by coating Al thin films on nano-structured Si surfaces and subsequent immersion in boiling water.
This process is relatively simple and available in large scale. Most of all, any kind of surface can be modified by this process as long as the materials can be survived in boiling water for 5 minutes. We tried this method on PDMS, glass, and silicon. As long as the adhesion of thin Al surface is stable, we could achieve the ultra-low-reflectance by the hierarchical thin film structures.
These hierarchical structures can be also coated with a low-surface-energy material which has higher water wetting angle (over 150 degree) and a very low contact angle hysteresis, implying a self-cleaning surface.
As a result, these surfaces have reflectance of less than 1.75 % in the wavelength of 600 nm and more.
9:00 AM - L9.50
Improving Metamaterial Refractive Index Sensors by Phase Interrogation Measurement
Hsin Cheng Lee 1 Ta Jen Yen 1 How-foo Chen 2
1National Tsing Hua University Hsinchu Taiwan2Yang Ming University Taipei Taiwan
Show AbstractMetamaterials have shown their remarkable applications in biosensing, bioimaging, and nanophotonics. Current studies regarding metamaterials as biosensor were only restricted in probing the extinction spectra (transmittance or reflectance), but however lack the complete understanding of metamaterials about its phase detection, limiting the performance in biosensing and bioimaging. Here, we experimentally demonstrate that a highly sensitive metamtaerial refractive index sensor by extrapolating its optical phase change instead of resonance spectra shift as the surrounding refractive index changes. To fabricate the metamaterial with resonance within near infrared, we use conventional electron beam lithography (ELS-7800, Elionix) and electron beam evaporation to deposit metallic layer followed by lift-off process. Next, to extrapolate the phase difference between TE and TM mode excitations, we apply a home-made optical setup and to excite metamaterials with different polarizations of incident light by Kretschmann-Raether configuration. With the freedom of scaling the metamaterials, we optimized the resonant wavelength of them to be close to the exciting laser so that the phase difference here becomes highly sensitive to the surrounding refractive index. The sensitivity of our metamaterials is around 17.1 rad/RIU, which is beyond the previous results of localized surface plasmonic resonance (LSPR) and metamaterial cases. We believe that phase interrogation is an alternative method in probing metamaterial resonance, and is able to complement the sensitivity insufficiency of metamaterial that interrogated by extinction spectra.
9:00 AM - L9.51
Printing of Sub-100 nm Plasmonic Metal Ring and Dot Arrays by Introducing New Stamping Platforms
Sang Ho Lee 1 2 Won Bae Kim 1 2
1Gwangju Institute of Science amp; Technology (GIST) Gwangju Republic of Korea2Gwangju Institute of Science and Technology (GIST) Gwangju Republic of Korea
Show AbstractSub-100 nm rings and dots, made of metal materials, are of considerable interest due to the unique properties from their peculiar morphologies and to their diverse applications in nanoscience and nanotechnology including optical devices, magnetic data storage, biological sensors, and catalysts for one-dimensional nanostructure growths [1-5]. For their practical implementation, the ability to fabricate uniformly controlled metal nanoring and nanodot arrays should be firmly established in effective processes. In this research, we report an efficient strategy to form sub-100 nm metal rings and dots by a printing method using new stamping platforms. Vertically aligned 1-dimensional carbon nanostructures of the ring-shaped and dot-featured tips, which are supported by the porous channels of anodic aluminum oxide templates, are used as stamps for transferring metal nanoring and nanodot patterns. Using the methodology, hexagonally oriented nanoscale metal ring and dot arrays such as gold, silver, platinum, copper, nickel, and aluminum are successfully printeded on various substrate substances in the laboratory environments. Moreover, the size, density, and interval of the printed metal nanorings and nanodots are able to be precisely controlled by modifying the geometries of the mother stamps. To this end, the characterization of the surface plasmonic resonance of the metal rings and dots are explicitly demonstrated by applying the printed metal nanoring and nanodot arrays.
Acknowledgement
This work was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future, Korea (0420-20120126) and by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2013029776 (Mid-career Researcher Program)).
References
[1] Aizpurua, J.; Hanarp, P.; Sutherland, D. S.; Kall, M.; Bryant, G. W.; de Abajo, F. J. G. Phys. Rev. Lett. 2003, 90, 057401.
[2] Banaee, M. G.; Crozier, K. B. Opt. Lett. 2010, 35, 760.
[3] Lodewijks, K.; Roy, W. V.; Borghs, G.; Lagae, L.; Dorpe, P. V. Nano Lett. 2012, 12, 1655.
[4] Lee, S. H.; Jo, G.; Park, W.; Lee, S. K.; Kim, Y. -S.; Cho, B. K.; Lee, T.; Kim, W. B. ACS Nano 2010, 4, 1829.
[5] Lee, S. H.; Cho, B.; Yoon, S.; Jeong, H.; Jon, S.; Jung, G. Y.; Cho, B. K.; Lee, T.; Kim, W. B. ACS Nano 2011, 5, 5543.
9:00 AM - L9.52
Structural and Optical Properties of TiO2 and TiO2/SiO2 Films Deposited by PECVD for Optical Applications
Dayu Li 1 Antoine Goullet 1 Michele Carette 1 Agnes Granier 1 Jean-pierre Landesman 2
1Institut des Matamp;#233;riaux Jean Rouxel (IMN-CNRS) Nantes France2Institut de Physique de Rennes (IPR-CNRS) Rennes France
Show AbstractTitanium dioxide (TiO2) is an attractive material for optical applications for its high refractive index and transmittance in the visible spectral range. PECVD is a low temperature deposition method which is compatible with silicon based semiconductor technologies and allows the accurate tuning of film properties. However, one of the main issues in the case of PECVD TiO2 films used for optical applications is to modify the columnar or heterogeneous morphologies which are usually observed [1-4].
In this study, the effect of ion energy from oxygen rich O2/titanium tetraisopropoxide (TIPT) inductively coupled radiofrequency plasmas on TiO2 film properties has been recently investigated. In addition, it is also shown that incorporating SiO2 phase in the TiO2 network from O2/TIPT/Hexamethyldisiloxane plasmas leads to more homogeneous films. The properties of TixSiyOz layers including morphology, crystallization and chemical composition were analyzed by TEM, SEM, AFM, XRD, Raman, FTIR, XPS and WDS. The film optical properties and additional structural information were extracted by properly modeling of the spectroscopic ellipsometry measurements, while the film growth process was monitored by kinetic ellipsometry.
TiO2 films of ~300 nm deposited at floating potential (Vf) exhibit a columnar morphology which consists of a dense layer near substrate, an intermediate gradient layer and a top roughness layer. A small amount of anatase is identified in this film. By appling a d.c. substrate bias of -50 V, the columnar structure can be eliminated, with a more homogenous morphology along the growth direction, and the appearance of the rutile phase. The refractive index (at 633 nm) of the whole film has been greatly increased up to 2.49 for the case of -50 V. Then for the composite film Ti0.35Si0.65O2, no crystalline phase can be evidenced, whereas a more homogenous morphology and smoother top surface are observed. The formation of new phase, Ti-O-Si indicates the strong interaction for chemical bonding. Although the refractive index is reduced to 1.71 compared to pure TiO2 films, the optical properties of mixed oxide layers are improved on the whole for waveguide corelayers.
Finally channel waveguides with TixSiyOz core layers have been fabricated and their optical propagation losses characterized by the cut-back method.
[1] D. Li, M. Carette, A. Granier, J. P. Landesman, A. Goullet, Thin Solid Films 522 (2012) 366-371.
[2] A. Granier, T. Begou, K. Makaoui, A. Soussou, B. Becirc;che, E. Gaviot, M.P. Besland, A. Goullet, Plasma Process. Polym., 6 (2009) S741-S745.
[3] A. Borras, J. R. Sanchez-Valencia, R. Widmer, V. J. Rico, A. Justo, A. R. Gonzalez-elipe, Crystal Growth & Design, 9 (2009) 2868-2876.
[4] F. Gracia, F. Yubero, J.P. Holgado, J.P. Espinos, A.R. Gonzalez-Elipe, T. Girardeau, Thin Solid films 500 (2006) 19-26.
9:00 AM - L9.53
Unique Electron-Transfer Effect in Heteronanostructured Pt@Ag Nanoparticles as Intrinsic Plasmonic Materials
Anh Thi Ngoc Dao 1 Derrick Mott 1 Shinya Maenosono 1
1Japan Advanced Institute of Science and Technology Nomi Japan
Show AbstractAg is one important metal which has novel optical properties in the nanoscale size regime. Ag nanoparticles show a wide range of colors corresponding to their localized surface plasmon resonance. The combination of Ag and other precious metals in a single particle has become an attractive technique to limit its disadvantages, such as easy oxidation, difficulty in aqueous synthesis, sensitive to ionic environment, etc. One of the primary highlights for this combination is the Pt-Ag system for not only plasmonic properties but also electro-catalytic activity. Among several heterostructures, the core@shell structure could be very interesting and beneficial in combination of the catalytic properties of Pt and plasmonic properties of Ag. However, there are still many challenges in the synthesis of core@shell structures. Galvanic replacement reaction poses a challenge to synthesizing Ag@Pt core@shell structures, while successful formation of Pt@Ag core@shell must overcome lattice mismatch and oxidation of the silver shell. This presentation focuses on our recent results in synthesis techniques and surface treatments of Pt@Ag core@shell NPs with controllable size and shell thickness. Moreover, the electronic-transfer effect is found to be a potential tool in designing and enhancing plasmonic properties of this system. Understanding the electronic structure and behavior of Pt@Ag nanoparticles will provide valuable insights into the fundamental mechanism of electron-transfer. Results are discussed in terms of UV-Vis, XRD, TEM, HR-TEM, EDS, XPS, and HAADF-STEM.
9:00 AM - L9.55
Eigenmode Analysis of Plasmonic Modes in Metal Nanoparticle Array and Their Coupling to Multilayered Medium
Jian-Wen Dong 1 Zi-Lan Deng 1
1Sun Yat-sen University Guangzhou China
Show AbstractPlasmon excitation of metal nanoparticles (MNPs) is widely studied in recent years. The plasmonic materials formed by MNPs can support subwavelength phenomena near optical frequencies and have strong near-field enhancement, promising for many plausible applications. To understand the underlying physics of the collective plasmonic response in the MNP array, an eigendecomposition method together with the free-standing Green function can be utilized to obtain the dispersion relations [1]. Localization characteristics and symmetric properties of a free-standing quasicrystalline MNP array [2, 3] have been investigated using the eigendecomposition method. It is found that spatial localized modes can either be leaky with out-of-plane radiation loss, or be very high fidelity. Apart from the free-standing case, the eigendecomposition method can also be applied to the MNP array sitting on multilayer, when we employed the layered Green function computed by Sommerfeld integration [4]. An effective eigenpolarizability, involving the collective effects of both the scattering of free-standing MNPs and the interaction between particles and layered structure, is well defined to characterize the dispersion relation and the mode quality of the plasmonic modes. In particular, we apply the new method to study the eigenmode of a one-dimensional periodic MNP chain near a metallic surface. It is demonstrated that the interplay between the surface plasmon at metal-dielectric interface and the localized plasmon in the chain enables strong modes splitting. The upper and lower modes show the in-phase and anti-phase properties between the MNPs and the metallic surface, respectively. In addition, for the polarization perpendicular to layer surface, high quality modes can be present inside the light cone even if the chain is open to air surrounding. A slow-light band is also predicted to exist as long as the layered medium supports surface plasmon mode that can couple to the chain mode.
Reference
1.K. H. Fung, and C. T. Chan, "Plasmonic modes in periodic metal nanoparticle chains: a direct dynamic eigenmode analysis," Opt. Lett., Vol. 32, No. 8, 973-975, 2007.
2.Jian-Wen Dong, K. H. Fung, C. T. Chan, and H.-Z. Wang, "Localization characteristics of two-dimensional quasicrystals consisting of metal nanoparticles," Phys. Rev. B, Vol. 80, No. 15, 155118, 2009.
3.Zi-Lan Deng, Z.-H. Li, Jian-Wen Dong, and H.-Z. Wang, "In-Plane Plasmonic Modes in a Quasicrystalline Array of Metal Nanoparticles," Plasmonics, Vol. 6, No. 3, 507-514, 2011.
4.Jian-Wen dong, and Zi-Lan Deng, "Direct eigenmode analysis of plasmonic modes in metal nanoparticle chain with layered medium," Accepted by Opt. Lett., Vol. xx, No., xx, 2013.
9:00 AM - L9.56
Which is the More Suitable Dopant (Neodymium or Erbium ions) in Waveguide Based on a Silica Matrix Containing Silicon Nanograins? A Theoretical Investigation of the Optical Gain
Alexandre Fafin 1 Julien Cardin 1 Fabrice Gourbilleau 1 Christian Dufour 1
1ENSICAEN UCBN CNRS CEA Caen France
Show AbstractWe search to amplify a signal into a strip-waveguide comprising an active layer co-doped with silicon nanograins and rare-earth ions stacked on a silica cladding layer and topped by a silica strip. The signal wavelength corresponds to the transition wavelength between two energy levels of a rare-earth ions. To achieve an efficient population inversion, the rare earth ions benefit from the indirect excitation via silicon nanograins which show an absorption cross section fourfold as high as the one of rare-earth ions. In order to study the influence of the type of rare earth on the optical gain, we consider two rare earth ions : neodymium ions Nd3+ for a signal wavelength at 1,06 mu;m and erbium ions Er3+ for a signal wavelength at 1,54 mu;m. The optical gain is expected to be different between Er3+ and Nd3+ doped waveguides since the former ion has a three-level electronic structure favoring the ground state re-absorption on contrary to the latter ion showing a four-level electronic structure.
To estimate the gain, we solve the Maxwell equations coupled to population rate equations and Lorentz-type polarization equations. We introduce an original algorithm based on the auxiliary-differential equation and finite difference time domain method (referred to as ADE-FDTD method). Using the conventional ADE-FDTD method we cannot have access to the steady state populations because there is a huge difference between characteristic time scales: the decay times of level populations (in the mu;s-ms range) and the period of the electromagnetic field (10-15s). Our algorithm allows to know the steady state levels populations as well as the spatial distribution of the guided field in the waveguide.
Populations and electromagnetic field maps in the waveguide will be presented considering two pumping schemes: co-propagation pumping and top pumping. The optical gain obtained with erbium ions and neodymium ions for those two pumping schemes will be discussed.
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Study of Surface Plasmon Polariton Behavior Using Incrementally-Constructed Nano-Hole Arrays
Patrick William Flanigan 1 Domenico Pacifici 1
1Brown University Providence USA
Show AbstractA plasmonic concentrator is a device that couples incident light to plasmon oscillations in noble metals with the goal of increasing the intensity of electromagnetic fields in local regions. One example is the nanohole array (NHA), a long-range pattern of shallow sub-wavelength holes that have been etched onto the surface of the metal. In an NHA, the incident light is converted to a surface plasmon polariton (SPP) mode that propagates along the dielectric / metal interface. Thin films resting on top NHA-etched silver films have demonstrated broadband absorption enhancement (compared to the case of an uncorrugated surface). The nature of the enhancement depends on the pattern, symmetry, and the characteristic hole-to-hole distance of the array, as those properties determine the nature of the constructive / destructive interference between counter-propagating SPP modes. This has immediate applications for thin film photovoltaics, as including an NHA beneath a thin absorbing layer will enhance absorption without sacrificing the benefits of using a thin film.
The authors&’ previous work studied absorption enhancement in terms of the entire array. However, there were still numerous issues related to SPP generation, propagation, and interference that were not well-understood; for example, how different parameters (wavelength, hole dimensions) can affect the scattering efficiency of the nanohole, how the SPP behaves in and around its parent nanohole, how an SPP reacts if it encounters a different nanohole, how SPPs interfere in short-range patterns, etc. To answer these questions, this report studies the plasmonic behavior of NHAs as they are built from the ground up - starting with a single hole, then moving to simple patterns, then to short-range arrays, then to long-range arrays. Both experimental and simulated data was utilized to characterize these systems. For the experimental part, NHAs were etched onto silver films (~102 nm thick) using Focused Ion Beam (FIB) milling; numerous characterization techniques were considered, including plasmonic interferometry and localized absorption / fluorescent measurements. These systems were also simulated using Finite Difference Time Domain (FDTD) software, as well as homemade simulation programs. In addition to providing a stronger understanding of the optical phenomena in plasmonic concentrators, this research will undoubtedly have a positive impact in real-world applications where efficient scattering and strong intensity concentrations are required.
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Systematic Investigation of the Gold Photoluminescence in Nanoscale Antennas
Toni Froehlich 1 Christian Schoenenberger 1 Michel Calame 1
1University of Basel Basel Switzerland
Show AbstractNanoscale dipole antennas are interesting systems to study electric field enhancement effects. Within the gap between both antenna arms, a very strong electric field arises, which can stimulate molecules present in the gap. This enhanced electric field is well suited for the optical characterization of molecules, such as in surface enhanced Raman scattering.
We study gold antennas which are lithographically fabricated on thermally oxidized silicon. A confocal laser microscope was used to investigate their single-photon photoluminescence (PL). The photoluminescence of a monopole antenna follows well a model proposed by Boyd et al. [1] if the energy peak position (Emax) is above the interband absorption edge (1.7-1.8 eV) of gold. The PL spectra of dipole antennas show a red-shift of Emax for decreasing gap sizes. We relate this behaviour to the increased coupling of individual arms via their optical near-field. The PL spectra are highly dependent on the shape of the antenna. For increased length or aspect ratio, we observe a decrease in the energy value Emax. We can accurately fit these spectra to the model [1] and estimate the dielectric properties of the environment. Interestingly for long antennas the spectra deviate from the model and show an additional peak. The latter peak show no geometrical dependence and remains at the energy value of the interband absorption edge. Our studies set the basis for future experiments on antennas embedding optically-active molecular compounds.
[1] G. T. Boyd et al., Physical Review B (33), 7923, 1986
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Ultrathin, Nanostructured Silicon Solar Cells for Large Area, Flexible Photovoltaics
Xuan Cao 1 Sung-Min Lee 1 Lesley Chan 1 Dongseok Kang 1 Jongseung Yoon 1 2
1University of Southern California Los Angeles USA2University of Southern California Los Angeles USA
Show AbstractThin monocrystalline silicon derived from wafer-based source materials represents a promising materials platform for high performance photovoltaic systems as it can provide superior materials properties compared to polycrystalline or amorphous silicon but also form ultrathin, microscale devices in a fashion that allows versatile choices of module substrates as well as high degrees of mechanical flexibility. The performance of ultrathin silicon solar cells, however, is inherently limited owing to their weak optical absorption associated with the indirect bandgap of silicon. Consequently, strategies of photon management to enhance the absorption of incident solar radiation and therefore improve the performance and cost-effectiveness of silicon solar cells have been of significant recent interest. Here we present experimental and computational studies of ultrathin, monocrystalline silicon solar cells with engineered photonic nanostructures as new materials platforms for high performance flexible photovoltaics, which can be deposited over large area on soft, deformable substrates to form lightweight, mechanically flexible solar modules. Arrays of ultrathin, nanostructured silicon solar cells as ‘printable&’ forms are fabricated directly from high quality bulk <111> wafer, in which various types of subwavelength photonic nanostructures are implemented softlithographically on the surface of silicon solar cells for optimized photon management and therefore enhanced photovoltaic performance with significantly reduced consumption of active materials.
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Ge Quantum Well Plasmon-Enhanced Quantum Confined Stark Effect Modulator
Papichaya Chaisakul 1 Delphine Marris-Morini 1 Nicolas Abadia 1 3 Jacopo Frigerio 2 Giovanni Isella 2 Daniel Chrastina 2 Segolene Olivier 3 Roch Espiau-de-lamaestre 3 Thomas Bernardin 4 Jean-Claude Weeber 4 Laurent Vivien 1
1Universitamp;#233; Paris-Sud Orsay France2Politecnico di Milano Como Italy3CEA-LETI Grenoble France4Universitamp;#233; de Bourgogne Dijon France
Show AbstractOptical interconnection is heavily investigated as an alternative to electrical interconnection for data communication between and on processor chips[1]. Optics is recognized as probably the only technologically-viable solution to overcome physical limitations of electronics in fulfilling the future chip scale data communication performance metrics. Nevertheless, despite intense research efforts, it is still unclear how the currently-proposed silicon-compatible optical solutions can meet the size, driving voltage, and energy consumption requirements for chip-scale interconnection. Due to weak electro-optical interaction, optical modulation schemes appear to require high applied voltages, long interaction length, and/or precise temperature control.
In this context, we theoretically and experimentally investigate a novel modulation concept on silicon (Si) based on the combination of quantum confinement and plasmon enhancement effects, with a view to realizing very efficient light modulation around a telecommunication wavelength of 1.3 µm. We exploit the strong modulation mechanism based on quantum-confined Stark effect (QCSE) in Ge/SiGe quantum wells (QWs) and use plasmonic enhancement to enable a large overlap between optical field, active Ge/SiGe materials, and electrical bias voltages. Firstly, we experimentally study the suitability of Ge/SiGe QWs on Si as the active material for a plasmon-enhanced optical modulator. We demonstrate that in QW structures absorption and modulation of light with transverse magnetic (TM) polarization is greatly enhanced due to favorable selection rules. A very sharp absorption peak, and strong light modulation in a Ge/SiGe QW waveguide are reported from photocurrent and transmission measurements. Later, we theoretically and experimentally study the plasmon propagation of a metal-Ge/SiGe QW interface. We design and fabricate a novel Ge/SiGe QW structure that allows maximized overlap between the plasmonic mode and the underlying Ge/SiGe QWs. Specifically, we employ 5 periods of a 10 nm Ge QW and a 10 nm Si0.15Ge0.85 barrier embedded in a p-i-n junction with only a 10 nm thick n type (~4×1019 cm 3) top layer, on which an Al contact is realized in order to support both TM plasmon mode propagation and electrical bias for Ge/SiGe QW absorption coefficient modulation. Electrical simulation and experimental I-V measurements confirm good electrical properties of the diodes based on this Ge/SiGe QW design. Finally, from the simulation, the structure gives a very effective optical modulation performance of 1.5 dB/µm with only 1 V bias. The optical loss is 2.5dB/µm which is largely due to metal absorption loss in the near infrared regime, and could be further improved through emerging plasmonic metals [2]. The latest experimental results on the propagation and modulation characteristics of the tested devices will be discussed at the conference. [1] D Miller, Proc IEEE 97 2009. [2] G Naik et al., Opt. Mat. Ex. 2 2012.
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Bragg Lattices of Plasmonic Nanoparticles in AlGaAs
Vladimir Chaldyshev 1 V. I. Ushanov 1 V. V. Preobrazhenskii 2 M. A. Putyato 2 B. R. Semyagin 2
1Ioffe Institute Saint Petersburg Russian Federation2Institute of Semiconductor Physics Novosibirsk Russian Federation
Show AbstractGaAs is the material of choice for a wide variety of optoelectronic application. The light-matter interaction in this material can be additionally enhanced by using metallic nanoparticles, which increase the local electromagnetic field. Creation of such nanoparticles is a big challenge, since the semiconductor technology, such as molecular-beam epitaxy (MBE) that is appropriate for mass production, does not allow one to directly grow the metallic nanoparticles in the film bulk.
In this paper we show the ability to create both random and periodic arrays of metallic nanoparticles in epitaxial AlGaAs via a two-step procedure based on the technology of low-temperature MBE. In this procedure an oversaturated crystalline AlGaAs medium is first grown with built-in precursors for the subsequent heterogeneous precipitation of the pure arsenic or AsSb alloy. The second step is the post-growth annealing, which allows us to control the size and density of the metallic nanoparticles.
Optical study of the samples shows a strong impact of the metallic nanoparticles on the reflectivity of the hybrid medium. It is important that the target Al content in the AlGaAs matrix and AsSb composition of the nanoinclusions have been adjusted to match the frequencies of the Bragg and plasmonic resonances within the optical window of the host matrix. In the case of a random system of the nanoparticles we observe an enhanced optical absorption, whereas in the case of the regular plasmonic lattices we recorded a strong Bragg reflection of the incident light.
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Integrating Biosensor and Imaging Array on One Chip
Cheng-Kuang Chen 1 Ta-Jen Yen 1
1National Tsing Hua University HsinChu Taiwan
Show AbstractOptical antenna is widely used for biosensing at its resonant frequency since resonant antenna can efficiently convert propagating electromagnetic wave into localized energy. The energy conversion efficiency is determined from antenna&’s resonant natures and sizes. In this study, we propose a multiresonant metamaterial simultaneously sensing the refractive index change and molecular vibration signal at fingerprint bands. We amplify the molecular signal by manipulating incident polarized light; and the measured angle selective enhancement is 1.4 of part;ΔR/part;theta; . We improve the signal collective ability by utilizing an metamaterial array; and the sensing performance of refractive index sensor gains to 2547 nm/RIU, as against 1180 nm/RIU of single meta-atom. In addition, this designed metamaterial can be considered as a multifunctional plasmonic pixel, tracing the pictures of the distribution of refractive indices and molecules with resolution of 20000 d.p.i. Thus, an image of label-free and coupler-free cell observation is demonstrated structurally and functionally, providing new feasibility for multifunctional biosensor and bioimaing design.
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Solution Processable Indolo[3,2-] Indole-Based Low Bandgap Small Molecules for High Performance Bulk Heterojunction Organic Solar Cell
Illhun Cho 1 Oh Kyu Kwon 1 Soo Young Park 1
1Seoul National University Seoul Republic of Korea
Show AbstractOver the past decade, organic semiconductors have attracted significant attention as a potential alternative of prevalent silicon based semiconductor for achieving low cost fabrication, easy processing, good mechanical property, flexibility, and so on. Aiming at the realistic performance, wide range of organic semiconductor materials have been designed and synthesized. In particular, heteroarene-containing fused aromatic systems have been intensively investigated as a backbone unit, for organic field-effect transistors (OFETs) and organic solar cells (OCSs), due to their high charge carrier mobility and environmental stability. Among various heteroaromatics, nitrogen-atom-containing fused aromatics are one of the most promising materials to ensure easy functionalization, high solubility and strong electron donating nature, which are of great importance in view of energy level tailoring for various organic electronic applications.
In this presentation, we report on a high-performance bulk heterojunction small molecule organic solar cell (SMOSC) using novel class of nitrogen containing fused aromatic system, indolo(3,2-b)indole (IDID). Among various IDID-based molecules synthesized in this work, ODIDID4T-OCA, which employs IDID as strong electron donor and octylcyanoacetate as strong electron acceptor, with PC61BM blend showed the organic photovoltaic device performance with 0.83 V of open circuit voltage (Voc), 9.03 mA cm-2 of short circuit current (Jsc), and 41% of fill factor (FF), resulting in 3.06% of power conversion efficiency (PCE) under the illumination of AM 1.5G, 100 mW cm-2.
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Electromagnetic Multiple Scattering Method for Layer-by-Layer Periodic Structures of Magnetized Spheres and Some Applications to Nonreciprocal Plasmonic Nanoarchitectures
Aristi Christofi 1 Nikolaos Stefanou 1
1National and Kapodistrian University of Athens Athens Greece
Show AbstractNonreciprocal photonic devices play a key role in optical communication and computing technologies because of their ability to eliminate cross-talk and feedback. In this perspective, topologically nontrivial phenomena, such as photonic chiral edge states, also attract increasing interest because they offer unique opportunities ensuring reflection-free one-way transport of light even in the presence of strong disorder. In general, spectral nonreciprocity is encountered in composite media that lack both space-inversion and time-reversal symmetries. Therefore, the development of accurate full electrodynamic computational methodologies that can describe such low-symmetry media is of crucial importance. The layer-multiple-scattering method is a rigorous and versatile method for studying photonic crystals consisting of nonoverlapping scatterers in a homogeneous host material. Contrary to traditional band-structure or time-domain techniques, it solves Maxwell equations in frequency domain and thus one can allow the electric permittivity and magnetic permeability of any of the constituent components to depend on the frequency, including also dissipative losses. A further advantage of the method is that it does not require periodicity in the direction perpendicular to the layers, which must only have the same two-dimensional periodicity. As a result, architectures without any inversion center, such as chiral structures, photonic crystal slabs on homogeneous plates and substrates, semi-infinite photonic crystals, etc. can be treated in a straightforward manner. On the other hand, time-reversal symmetry is absent in gyrotropic materials under the action of a static, uniform magnetic field. In the present communication we present an extension of the layer-multiple-scattering method to photonic crystals of gyrotropic spheres and demonstrate its applicability on different nonreciprocal architectures, namely three-dimensional chiral structures, as well as surfaces and layers of fcc crystals of plasma spheres in a static, uniform magnetic field. A detailed analysis of relevant photonic dispersion diagrams and transmission spectra, in the light of group theory, provides a consistent interpretation of some intriguing features and effects like Dirac points, polarization-dependent transmission, as well as band splitting and nonreciprocal optical response. In particular, it is shown that, in a bulk helical structure of plasma spheres, nonreciprocal light transport takes place along the helix axis in the Faraday geometry, i.e., under a magnetic field oriented along the propagation direction. On the other hand, at the (001) surface of a semi-infinite fcc crystal of plasma spheres or at a monolayer of it deposited on a substrate, under an in-plane magnetic field, nonreciprocal propagation is demonstrated in the Voigt (Cotton-Mouton) geometry, i.e., perpendicular to the direction of the magnetic field.
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Plasmonic Gas Sensors: Comparison between Localized Surface Plasmon Resonance and Surface Plasmon Polariton VOC Sensor
Michela Cittadini 1 Laura Brigo 1 Enrico Gazzola 2 Flippo Romanato 2 Massimo Guglielmi 1 Giovanna Brusatin 1 Alessandro Martucci 1
1Universitamp;#224; Degli Studi di Padova Padova Italy2Universitamp;#224; degli studi di Padova Padova Italy
Show AbstractIn this work we compared two different optical techniques to sense Volatile Organic Compounds (VOC). VOC are organic chemicals with high vapor pressure at room temperature. This results in a large evaporation or sublimation from the liquid or solid form into the surrounding air. Some VOCs are dangerous to human health or cause harm to the environment.
Herein we present plasmonic VOC sensors, working at room temperature, obtained coupling TiO2-Pt nanocomposite films with Au nanoparticles (NPs) or depositing the same TiO2-Pt nanocomposite film on a sinusoidal surface plasmon metallic grating (SPG).
In the first case the Au Localized Surface Plasmon Resonance (LSPR) peak is used as an optical probe for the VOC detection as it is well know that its position, shape and intensity depends on the environments and/or the electron densities.
In the second case the sensitive material is deposited on a sinusoidal grating constituted by a gold thin layer embedded between two dielectric, one of which is the sensitive layer. The surface plasmon polaritons (SPPs) generated at the two metal-dielectric interfaces, result in two physical coupled modes: the long range SPPs (LRSPPs) and the short range SPPs (SRSPPs). The metal layer is in contact with the environment through the sensitive material, which changes its dielectric properties upon interaction with the target gases. Any change in the refractive index of the dielectric environment modifies the resonance conditions to excite the SPP.
Experimental and theoretical characterizations of the optical properties of the plasmonic devices are reported.
The aim of the comparison between localized and propagating SPR based technique with VOC is to investigate if the change of the refractive index of the sensitive film in response to the analyte is only due to the substitution of the air in the pores with the VOC, which has an higher refractive index, or can be connected to an exchange of electrons between the VOC molecules and the metal oxide matrix. We also want to find out which one of the two techniques is the best to sense this electron interaction, avoiding the refractive index effect.
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Enhancement of Nonlinear Optical Harmonic Generation in Gold Nanorods
Matthew J. Cote 1 Kevin Regan 1 Olalekan Afuye 2 Michael Durst 2
1Bates College Lewiston USA2Bates College Lewiston USA
Show AbstractPlasmonic nanostructures show great technological promise with applications including bioimaging, chemical sensing, solar cell enhancement, and fast hybrid photonic-electronic devices. Realizing their full potential will require convenient means for characterizing their optical and electronic properties and comparing those properties to theoretical predictions. Conventional optical imaging techniques can provide important spectroscopic information about plasmonic nanostructures but they lack the spatial resolution to probe nanometer-scale morphological and geometric features that have been shown to affect plasmonic behavior strongly. Nonlinear optical behavior, on the other hand, has been shown to be highly sensitive to those sub-wavelength size features [1].
Nonlinear optical imaging of metallic nanoparticles was previously demonstrated through second harmonic generation (SHG) [1-3], third harmonic generation (THG) [4,5], and two-photon luminescence (TPL) [6]. The nonlinearity stems from the localized surface plasmons resonant with the optical field. The frequencies at which the resonances occur within individual nanoparticles depend on the nanoparticle size, shape, and orientation, as well as the refractive index of the surrounding medium. The plasmon resonance can be strongly affected by interactions with nearby plasmonic nanoparticles. This coupling has been shown to enhance SHG signals from nanoantennas [1], periodic arrays of gold nanospheres [7], and gold nanospheres with controllable separations [8].
Through a combination of total internal reflection darkfield microscopy and nonlinear optical microscopy and spectroscopy, we survey the SHG, THG, and TPL signals from self-assembled gold nanorod structures. We then use scanning electron microscopy to correlate nonlinear optical signatures with the morphologies of individual nanorods and the geometries of nanorod assemblies. The nonlinear optical measurements are made using an ultrafast near-infrared laser whose second and third harmonics are resonant with the gold nanorods&’ longitudinal and transverse plasmons, respectively.
[1] J. Butet, K. Thyagarajan, and O. J. F. Martin. Nano Lett. 13 (4), 1787-1792 (2013).
[2] C. Hubert, L. Billot, P. M. Adam, R. Bachelot, P. Royer, J. Grand, D. Gindre, K. D. Dorkenoo, and A. Fort. Appl. Phys. Lett. 90 (18), 181105-1-3, (2007).
[3] E. J. Smythe, E. Cubukcu, and F. Capasso. Opt. Exp. 15, 7439-7447 (2007).
[4] M. Lippitz, M. A. van Dijk, and M. Orrit. Nano Lett. 5 (4), 799-802 (2005).
[5] O. Schwartz and D. Oron. Nano Lett. 9 (12), 4093-4097, 2009.
[6] D. Yelin, D. Oron, S. Thiberge, E. Moses, and Y. Silberberg. Opt. Exp. 11, 1385-91 (2003).
[7] B. L.Wang, M. L. Ren, J. F. Li, and Z. Y. Li. J. Appl. Phys. 112, 083102 (2012).
[8] A. Slablab, L. Le Xuan, M. Zielinski, Y. de Wilde, V. Jacques, D. Chauvat, and J. F. Roch. Opt. Exp. 20, 220-227 (2012).
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How Planar Defects Affect the Optical Properties of Silver Nanostructures?
Xue Ben 1 Harold S Park 1
1Boston University Boston USA
Show AbstractThe optical properties of small complex metal nanostructures, gold and silver, have been investigated in great detail over the past two decade. Specifically, these two metals exhibit localized surface plasmon resonance (LSPR), which is a collective oscillation of the conduction electrons when excited by electromagnetic radiation within the visible spectrum.
However, metal nanostructures with defects are hardly studied, due to that the ability to resolve the effects of the defects on the optical properties depends crucially on having a computational method in which the discrete positions of all atoms are explicitly represented, which cannot be addressed by conventional numerical methodologies(Discrete Dipole Approximation, Finite Element Method, Finite-Difference-Time-Domain Method, etc).
In this presentation, we report a computational atomistic electrodynamics investigation of the effects of planar defects on the optical properties of silver nanocubes, where the planar defects we considered are different surface orientations, twins, partial dislocations and full dislocations. Our simulation results show that for nanocubes smaller than about 3 nm, the optical response is very sensitive to the specific surface structure resulting from the defects. However, the sensitivity, as measured by shifts in the plasmon resonance wavelength, is strongly reduced at larger sizes, due to the decreasing importance of surface effects, even when the majority of the atomic deformation due to the crystal defects is contained within the interior of the nanocube. Overall, this systematic study suggests that the effects of individual crystalline defects on the optical properties of nanostructures can be safely ignored for nanostructure sizes larger than about 5 nm. This optomechanical coupling effects will have wide application in biosensing, mechanical strain sensing, and optical tagging and detection.
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White Light Emission from Y2O3 Nano-Powders Induced by a Laser Diode Beam
Gokhan Bilir 1 3 John Collins 2 Gonul Ozen 1 Baldassare Di Bartolo 3
1Istanbul Technical University Istanbul Turkey2Wheaton College Norton USA3Boston College Chestnut Hill USA
Show AbstractWe have achieved the production of white light by illuminating nominally pure Y2O3 nano-powder samples with the beam of a laser diode operating at 803.5 nm with an output power of 3 watt. Some nano-samples (~20 nm) were prepared by us with a method based on the thermal decomposition of alginate gels. Some other samples were commercially available Y2O3 nano-powders (<50 nm) purchased from Sigma Aldrich. The white light spectrum ranged from 450 to 850 nm. Its intensity was not depending on the temperature of the samples, but was strongly dependent on pressure, with higher values at low pressure. We shall present some hypothesis on the mechanism responsible for this effect.
1. Department of Physics, Istanbul Technical University, Istanbul, Turkey
2. Department of Physics, Wheaton College, Norton, MA USA
3. Department of Physics, Boston College, Chestnut Hill, MA, USA
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Dyakonov Surface Waves: An Enabling Mechanism for `Piezo-Opticrsquo; Stress Sensing
Carlos M Bledt 1 Jimmy Xu 1
1Brown University Providence USA
Show AbstractDyakonov Surface Waves (DSWs) are novel surface waves capable of propagating at interfaces between two lossless dielectric media in which at least one medium exhibits optical anisotropy and where the relative refractive indices of the two media meet specific criteria. DSWs were first predicted to exist by M. I. Dyakonov in 1988 at an interface between two dielectric media where the first is an isotropic cladding material and the second is an uniaxial anisotropic substrate material meeting the DSW propagation condition εs,o < εc < εs,e. Since their first prediction, DSWs have been theoretically shown to exist in a number of additional dielectric media interface systems. However, to date their exploration has remained largely theoretical and limited to basic principles rather than their implementation in applications. As a first attempt to advance the basic science of DSWs into applications, this study explores the desirable low-loss, highly localized, and self-collimating waveguiding character of DSWs for the development of highly sensitive next-generation optomechanical sensors. The inherent extreme sensitivity of DSWs on the dielectric constants of the constituent system media results in optically observable changes in the DSW propagation characteristics upon the application of an external mechanical stimulus, instituting the functional mechanism for the proposed novel stress sensing devices. Such an effect is analogous to piezoelectric transduction, yet being optical in read-out, the proposed DSW based mechanism can be thought of as novel ‘piezo-optic&’ sensing. As such it breaks an inherent speed limit originating from the high impedance of electrical read-out in piezoelectric transducers. After establishing the necessary conditions for DSW propagation and the essential DSW propagation properties, a number of feasible isotropic / uniaxial birefringent DSW structures of interest for use in stress sensing applications are introduced and thoroughly investigated. Through theoretical analysis and simulations, the effects of dynamic stress stimuli on the DSW propagating characteristics are explored and presented. To achieve this, in-depth theoretical modeling of the proposed sensing device structures is performed, merging DSW and tensor analysis to predict the properties, benefits, and possible limitations of these systems. Furthermore, discussion of the proposed DSW based sensors is extended to practice and eventual device implementation. The expected benefits of DSW based sensing devices over current piezoelectric sensing devices, including increased sensitivity and speed, miniaturization in scale, and lower power consumption, are also presented.
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Variable Energy Excitation and Simulation of Hybrid Silicon-Metal Plasmonic Nanocavities
Carlos Aspetti 1 Chang-Hee Cho 2 Ritesh Agarwal 1
1University of Pennsylvania Philadelphia USA2Daegu Gyeongbuk Institute of Science amp; Technology Daegu Republic of Korea
Show AbstractSurface plasmon-based optics allows the manipulation of optical properties of matter at the nanoscale with length scales far below the diffraction limit. Recently, the resonant interfacing of surface plasmons with active materials in confined nanocavity architectures resulted in highly non-thermalized and efficient light emission from semiconductor nanowires. Here, we present results on photoluminescence studies performed at variable excitation energies on large (~150 nm) silicon nanowires coupled with metal nanocavities, which provides strong evidence for a hot-photoluminescence process in which individual hot (non-thermalized)-states are independent of the excitation wavelength, but the overall emission bandwidth is restricted by silicon&’s electronic structure. Size-dependent and excitation energy-dependent experimental photoluminescence measurements are coupled with FDTD simulations of the cavity modes. By examining cavity modes of the silicon-based nanocavities, at the excitation and emission channels, we are able to gain insights into the role of both surface plasmon polariton modes and localized surface plasmon resonances in modulating the broad spectral characteristics of the emission. Our results show that nanocavity plasmons can be utilized to efficiently produce and extract light from a “dark” material such as silicon, which typically has a very low emission quantum yield.
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Optical Design of Photo-Electrochemical Devices
Miguel Anaya 1 Mauricio E. Calvo 1 Jose Miguel Luque 1 Hernan Miguez 1
1Consejo Superior de Investigaciones Cientificas Sevilla Spain
Show AbstractDevices in which sunlight is used as energy source to produce photon-to-electron conversion have been continually growing in importance in the last years (i.e. dye solar cells). The use of new compounds needs the proposal of novel optical architectures to improve the efficiency[1] or to modify the external characteristics of these devices.[2] We employ theoretical models based on transfer matrix method to describe light behavior into these types of layered structures[3] and to design new ones in which we can selectively control light confinement. The use of porous one dimensional photonic crystals allows us not only to spectrally enhance the photocurrent resonances but also to change the aspect.[4] We foresee the structures that we present could allow the development of photo-electrochemical devices with finer spectral control over light absorption and different aesthetic performances.
References
[1] Colodrero, S.; Forneli, A.; Lopez-Lopez, C.; Pelleja, L.; Miguez, H.; Palomares, E.; Adv. Func. Mat. 2012, 22, 1303-1310.
[2] Lozano, G.; Colodrero, S.; Caulier, O.; Calvo, M.E.; Miguez, H.; J. Phys. Chem. C 2010, 114, 3681-3687.
[3] Colonna, D.; Colodrero, S.; Lindstron, H.; Di Carlo, A.; Miguez, H.; Energy Environ. Sci. 2012, 116, (21), 11426-11433.
[4] Anaya, M; Calvo, M.E.; Luque, J.M.; Miguez, H.; J. Am. Chem. Soc. 2013, DOI: 10.1021/ja401096k.
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Metallic Nanoparticles Produced in the Core of Femtosecond Laser Micromachined Waveguides
Juliana Mara Pinto Almeida 1 Paulo H D Ferreira 1 Antonio C Hernandes 1 Cleber R Mendonca 1
1University of Sao Paulo Sao Carlos Brazil
Show AbstractFemtosecond laser micromachining has been used to induce permanent changes in the bulk of transparent materials in order to produce three-dimensional microstructures. Since the process involves nonlinear optical interactions, the material modification occurs only around the focal volume. Thus, surface damages are avoided by focusing the laser beam into the material bulk. Moving the sample regarding the laser focus it is possible to change the material properties with high spatial accuracy. Such proprieties can be effective changed by the formation of metallic nanoparticles during the irradiation process. Once metallic nanoparticles (NPs) exhibit ultrafast response times and high third-order nonlinearities, their spatial control in the micrometer scale can be essential for the development of all-optical devices. Although waveguides, splitters, amplifiers and resonators have been demonstrated using different techniques and materials, 3D-protonic microstructures containing metallic NPs have received little attention despite their importance for integrated optics. In this sense, the purpose of the current study was to produce waveguide containing metallic NPs in its core using femtosecond laser micromachining. To achieve this goal, we used copper doped borosilicate glass which was irradiated with a Ti: Sapphire laser, operating at 5 MHz with pulses of 50 fs at 800 nm (40 nm bandwidth). The laser pulses were focused beneath the sample surface through a microscope objective, while the sample was moved by a xyz stage at constant speed. Using an input energy of 74nJ and 10 mu;m/s of scan speed, we indentified the formation of metallic copper nanoparticles in the irradiated regions through the surface plasmon resonance band at 570 nm in the absorption spectrum. By doing so, cylindrical waveguides with a core of metallic copper NPs were obtained throughout the sample (3 mm), which have a transversal profile of 5 mu;m of diameter. An optical system, based on a He-Ne laser and microscope objectives, was used to characterize the propagation modes and losses of the light guided. Near-field output images showed a multimode waveguide at 633 nm. In this case, the propagation loss was estimated to be about 0.4 dB/mm. Single mode waveguides were also produced by changing the irradiation conditions. In summary, we have shown the fabrication of waveguides containing metallic copper NPs in glass using femtosecond laser micromachining. Low losses of the multimode and single mode propagation were obtained, which is a promising result for practical applications.
9:00 AM - L9.76
Enhanced Photoluminescence from Rare Earth Ions (Eu3+, Dy3+, Sm3+) in Zeolites by Co-Doping Silver Clusters
Sachu Ronggui 1 Kenji Imakita 1 Minoru Fujii 1
1Kobe University Kobe Japan
Show AbstractRare-earth (RE) ions are well-known phosphorescent materials, which are practically used for many kinds of commodities, such as lighting, display, laser and so on. However, the optical absorption of RE ions is very weak due to the forbidden nature of intra-4f transitions. Sensitization by an energy transfer process is an attractive way to obtain efficient emission from RE ions. Recently, Eichelbaum et al. reported that photoluminescence (PL) of RE ions in silicate glasses is significantly enhanced by metal clusters precipitated by synchrotron X-ray irradiation. The enhancement was found to be caused by energy transfer from metal clusters to RE ions. Their results indicate that metal clusters have a great potential to enhance the effective excitation cross section of RE ions.
In this work, we focus on zeolite as a host material to study the sensitization of RE ions. Zeolite, possessing a cage structure consisting of orthosilicate ion (SiO4 4-) and orthoaluminate ion (AlO4 5-) structural units, is one of the most suitable host materials for the formation of metal clusters. Metal clusters are known to be chemically stable in the nano-sized pores in the cage, and can be formed by a simple ion exchange process followed by a thermal treatment. In this study, the effect of silver (Ag) clusters on the PL properties of RE ions in zeolite was investigated for the first time. We show that PL of europium (Eu) ions in the visible region can be significantly enhanced by Ag clusters in zeolite Y, due to the photosensitization effect. We also studied the sensitization of dysprosium (Dy) and samarium (Sm) in zeolite A and observed similar PL enhancement by Ag co-doping. The results suggest that zeolite is a promising host material for the sensitization of RE ions by metal clusters or ions.
9:00 AM - L9.77
Fluorescence-Intensity Enhancement of Dye Molecules by Si Microarray
Ken-ichi Saitow 1 2 Masanori Sakamoto 2 Hironori Tamamitsu 2
1Hiroshima University Higashi Hiroshima Japan2Hiroshima University Higashi Hiroshima Japan
Show AbstractWhen a molecule near the surface is excited by the large localized electric field, its Raman and/or fluorescence intensities are enhanced dramatically. These processes have generally occurred on the noble metal surface with nanostructure. However, one of the most crucial issues for fluorescence intensity enhancement is how to reduce fluorescence-intensity quenching via inherent energy transfer from excited molecules to the substrate metal. That is, when molecules are within a few tens nanometer from the metal surface, the energy of the molecules in an excited electronic state has to be effectively transferred to an electronic state in the metal band structure, which has a high density of state. Therefore, to obtain a large EF, it is extremely important to inhibit energy-transfer and fluorescence-quenching processes. One of the good candidates for reducing energy transfer is to use an indirect semiconductor as an enhancement substrate. Silicon (Si) is a typical indirect-transition semiconductor. In addition, there are the other good properties; (1) it is nontoxic, (2) it exists in great abundance, and (3) it is inexpensive. Therefore, if the enhancement effect is observed with Si, the development of economical enhancement substrates formed of a nontoxic quench-free material would be possible. Here, we show whether the fluorescence intensity of dye molecules can be enhanced using a silicon microarray substrate, synthesized using chemical etching together with silver ion. The fluorescence intensity of crystal violet (CV) solution was investigated using the Si array substrate. As a result, we obtained an enhancement factor of 30, which is as large as typical enhancement factors of noble-metal nanoparticles for fluorescence intensity enhancement of dye molecules. In addition, the repeatability for enhancement effect was very good.
9:00 AM - L9.78
First Principles Investigation of Ru Based Dyes for DSSC
Nikhil Nagesh Patil 1 Sumit Saxena 1
1Indian Institute of Technology Bombay Mumbai India
Show AbstractDye sensitized solar cells are one of the youngest members of the solar cell family and have been inspired by mother nature&’s process of photosynthesis, which involves separate process for light absorption and charge separation. Sensitizers play a crucial role in higher photon to electricity conversion which in turn dictates the efficiency of the dye sensitized solar cells. Classical ruthenium based dyes have been used and a lot of effort has been made to enhance the efficiency of these solar cells by modifying these dyes. Recently influence of mesityl, di-tert-butyl and/or tri-iso-propyl phenyl moieties with or without conjugation of ancillary bipyridyl ligand for improved photovoltaic parameters of dye sensitized solar cells have been reported and a record efficiency of 11.4% has been claimed and certified. The underlying mechanism resulting in these enhanced efficiencies is not well understood. In this pursuit results providing insight into charge transfer mechanism for different ruthenium based complexes obtained using first principles time dependent density functional theory will be discussed.
9:00 AM - L9.79
Preparation of Metal Mesh Device Sensor for Detection of Particulate Matters in Air
Hirokazu Seto 1 Seiji Kamba 2 Takashi Kondo 2 Yuichi Ogawa 3 Yu Hoshino 1 Yoshiko Miura 1
1Kyushu University Fukuoka Japan2Murata Manufacturing Company Nagaokakyo Japan3Kyoto University Kyoto Japan
Show AbstractThe harmful effects of particulate matter (PM) on health have manifested as immunological disorders like asthma, tumorigenicity, and heavy-metal toxicity, and, therefore, air pollution is a very serious issue. The World Health Organization (WHO) has compiled air quality guidelines, wherein acceptable environmental levels of various air pollutants are reoprted. PM is classified according to size. PM2.5 and PM10 are defined as fine particles which are permeated through a grading device with a 50% of sampling efficiency at a diameter of 2.5 mu;m (median diameter; 2.5 mu;m) and which are permeated through a grading device with a 50% of sampling efficiency at a diameter of 10 mu;m (median diameter; 10 mu;m), respectively. Additionally, fine particles with a median diameter ca. 7 mu;m, which are permeated through a grading device with a 100% of sampling efficiency at a diameter of 10 mu;m, are referred to as suspended particulate matter (SPM) in Japan. Environmental limit for the mass concentration of PM2.5 has been strictly established at less than 15 mu;g/m3 as an annual average with less than 35 mu;g/m3 as a daily average, and that of SPM has been established at less than 0.10 mg/m3 as a daily average with less than 0.20 mg/m3 as an hourly average. A rapid analytical technique with a wide detection range for PM is required.
In the 1960s, metal mesh devices (MMDs) with two-dimensional periodic structures were found to exhibit frequency selectivity, and could be used as band-pass filters. The frequency selectivity depends on the size characteristics of the MMDs. The electric field is localized around the surface of the MMD, and as a result a dipped structure is observed in the transmittance infrared (IR) spectrum of the MMD. Intrusion of matter into the electric field localized on the surface of the MMD leads to a shift in the dipped frequency. Therefore, MMDs is applied as a sensor. In this study, the detection of PM in air was performed using MMD sensing, where the MMDs functioned both as a membrane filter for the collection of PM and as a band-pass filter for the detection of PM.
A 100 THz-operated MMD with a 2.6 mu;m grid interval and a 1.8 mu;m opening length was used for the collection and detection of SPM. After the recovery of air through the MMD, the collection of SPM on the MMD was observed by optical microscope. Changes in dipped frequency in the transmittance spectra of the MMD containing SPM were found to have a linear relationship to the mass concentration of SPM, which was determined by the Ministry of the Environment in Japan, with a high coefficient of determination. The MMD sensor enabled the collection and detection of PM.
9:00 AM - L9.80
Effective Light Trapping in Amorphous Hydrogenated Silicon by Embedding Metal Nano-Particles for Photo-Voltaic Applications
Habibuddin Shaik 1 Sundar Murthy M 2 Mohan Rao G 1 Swaroop Ganguly 2
1Indian Institute of Science Bangalore India2Indian Institute of Technology Bombay India
Show AbstractEffective light trapping inside active layer is essential to enhance the performance of the photovoltaic devices at lower active layer thicknesses. We took the advantage of light scattering by metal nanoparticle and strong local field enhancement due to localized surface plasmon resonance around the metal nanoparticle by embedding inside a semiconducting material. By placing spherical silver (Ag) nanoparticles inside hydrogenated amorphous silicon (a-Si:H), we measured the photo-current enhancement due to enhanced optical absorption. We analyzed the effect of size and position (depth) of metal nanoparticles on photo-current enhancement. 15nm, 25nm and 50nm silver (Ag) particle are embedded in a:Si:H and photo current are measured. The simulation results were also matching with the experimental results. We found that 15nm particles are enhancing the photo current about 2 times the reference structure when placed in the a-Si:H. Enhancement may be larger for larger particles by keeping constant coverage area rather than constant particle density.
9:00 AM - L9.81
Centrifugal Shape Sorting and Optical Response of Polyhedral Plasmonic Nanoparticles
Yu Jin Shin 1 Mark Hersam 1
1Northwestern University Evanston USA
Show AbstractMetallic nanostructures are of high interest because their optical properties can be tuned throughout the visible and near-infrared portions of the electromagnetic spectrum by adjusting nanoparticle shape, size, composition, and local dielectric environment. In particular, the localized surface plasmon resonance (LSPR) properties of plasmonic nanoparticles have shown promising applications in chemical and biological sensing, waveguiding, single particle tracking, and surface enhanced Raman spectroscopy (SERS).
Since inhomogeneous broadening from nanoparticle size and shape variations causes an increase in the linewidth of bulk LSPR spectra, monodispersity of the nanoparticle population is critical for optimal performance in LSPR-based devices and sensors. Towards that end, previous studies have focused on obtaining more homogeneous nanoparticle populations via post-synthetic separation techniques including size exclusion chromatography, gel electrophoresis, and centrifugation. Among these methods, density gradient centrifugation has proven to be particularly successful, resulting in narrow distributions of gold nanoparticle diameters, shapes, and aggregation state.
The shape-dependent optical properties of metal nanostructures have also motivated efforts to realize new nanoparticle shapes via novel synthetic routes and to correlate nanoparticle structure with plasmonic behavior. Among available plasmonic nanoparticle shapes, gold bipyramids (BPs) are of interest due to their sharp tips that lead to strong localized field enhancement and high sensitivity to the surrounding dielectric environment. In particular, {110}-faceted gold BPs consisting of two triangular pyramids joined by a (111) twin plane, have shown high stability and resistance against oxidative etching compared to other structures with near-infrared resonances. Despite their potential, relatively few reports have studied the optical properties of small BPs (i.e., BPs with edge lengths in the sub-100 nm range that show LSPR at visible wavelengths) due to their relatively low synthetic yields (~30% BPs).
Herein, we have developed a centrifugal route for separating sub-100nm, polyhedral plasmonic nanostructures, namely rhombid dodecahedra (RD) and triangular BPs, which form simultaneously during synthesis and cannot be separated via conventional filtration methods. Centrifugation in a shallow density gradient allows the enrichment of the original minority BP species, which enables a 2.5 times increase in refractive index sensitivity compared to the as-synthesized, unsorted mixture of plasmonic structures. Furthermore, these ensemble measurements are further corroborated by single-particle LSPR spectra with the distribution of the plasmon resonance energies of the sorted particles quantified via dark-field optical microscopy.
9:00 AM - L9.82
Metamaterial-Mirrors in Optoelectronic Devices
Majid Esfandyarpour 1 Erik C Garnett 2 Mark L Brongersma 1
1Stanford University Stanford USA2FOM Institute AMOLF Amsterdam Netherlands
Show AbstractThe phase reversal that occurs when light reflects from a metallic mirror produces a standing wave profile that features a reduced light intensity and thus light-matter interaction near its surface. This is highly undesirable in optoelectronic devices that employ metal films as electrical contacts and optical mirrors; it dictates a minimum spacing between the metal and active semiconductor layers in a device and poses a fundamental limit to their practical thickness. Here, we illustrate how a metamaterial-mirror can be created in the visible spectral range whose reflection phase is tunable from that of a perfect electric mirror (phi;=π) to a perfect magnetic mirror (phi;=0). This is accomplished by nanopatterning a conventional mirror surface with subwavelength grooves. We then demonstrate the benefits of implementing such a mirror in a real device. Specifically, we show how light absorption and photocurrent generation in a sub-100-nm active semiconductor layer can substantially be enhanced over a broad spectral band.
9:00 AM - L9.83
Self-Assembled Plasmonic Nanostructures Using Peptide Dendrimer Amphiphiles
Joseph Slocik 1 Lawrence Drummy 1 Rajesh R Naik 1
1AFRL WPAFB USA
Show AbstractBiology enables solutions to many problems encountered in materials science in the form of exceptional molecular and genetic level control, chemical specificity, and the availability of a large diversity of highly functional biological templates. Therefore, to date, there has been extensive effort aimed at mimicking biological systems for the synthesis, functionalization, and self-assembly of extended nanomaterial structures. Notably, one approach has been to utilize peptide amphipiles for the controlled synthesis and self-assembly of 1-D nanoparticle helical structures. In this study, we have extended this approach by including gold-binding peptide dendrimer amphiphile with multiple peptide copies. Using this configuration of peptides and alkyl chains, we have increased the binding affinity to gold and created self-assembled helical nanoparticle ribbons which exhibited tunable plasmonic, chirooptical, and catalytic activity.
9:00 AM - L9.84
Tunable MEMS Plasmonic Microscope
Thomas Stark 1 Ahmet Serdar Yilmaz 1 Jackson Chang 1 Matthias Imboden 1 David Bishop 1 Selim Uenlue 1
1Boston University Boston USA
Show AbstractThe plasmonic response of metallic nanoparticles depends upon the particle composition, size, shape, surrounding medium, and electromagnetic field coupling to neighboring particles and surfaces [1]. Localized surface plasmon (LSP) resonances are sensitive to changes in the surrounding dielectric medium, a phenomenon that has been widely studied and successfully used as an ultra-sensitive sensing platform [2], [3]. Here we present the mechanical components of a MEMS-based, micron-scale plasmonic microscope which utilizes the LSP response to map local variations in the dielectric properties of a sample.
We developed a MEMS actuator that can precisely scan a pair of plasmonic nanoparticles over a sample. By optically exciting plasmon modes, performing a scan, and measuring the change in intensity of the plasmonic response, we will map local changes in the dielectric properties of the sample. The device consists of two polycrystalline silicon probes, each containing a plasmonic nanoparticle. Using electrostatic comb drives and plates, we can independently actuate each tip and control the interparticle separation with a precision of several nm [4]. We can then move the pair of nanoparticles along two orthogonal axes, one in the plane of the device (x) and one out of the plane (z). A moveable stage below the nanoparticles enables us to position the sample relative to the nanoparticles along the y-axis. Combining these degrees of freedom, the device enables us to spatially scan the nanoparticles over a sample area and forms the mechanical basis of a micron-scale plasmonic microscope.
[1] Murray, A.; Barnes, W. L., Nano Lett. 19, 3771-3782 (2007).
[2] Mock, J. J.; Smith, D. R.; Sheldon, S. Nano Lett. 3 (4), 485-491 (2003).
[3] Roh, S.; Chung, T.; Lee, B. Sensors. 11, 1565-1588 (2011).
[4] Imboden, M.; Han, H.; Chang, J.; Pardo, F.; Bolle, C.; Lowell, E.; Bishop, D. J.; Nano Lett. (2013) to be published.
9:00 AM - L9.85
Surface Plasmon Enhanced Photoluminescence of ZnO Nanorods by 1D and 2D Metal Gratings
Jie Tang 1 2 Liyuan Deng 1 Jian Huang 1 Soo Jin Chua 1 2 3
1National University of Singapore Singapore Singapore2National University of Singapore Singapore Singapore3National University of Singapore Singapore Singapore
Show AbstractZinc oxide (ZnO) is an attractive semiconductor for UV optoelectronic devices such as LEDs, photodetectors, and laser diodes, benefiting from its large bandgap (3.37eV) and high exciton binding energy (60meV). In order to fully realize the potential of ZnO for these applications, great efforts have been put into the study of fundamental optoelectronic properties since 1940s. However, in most cases, the light emission efficiency is low as a large number of carriers are trapped by defects or impurities inside luminescence centers. Recently, the resonant coupling between spontaneous emission of ZnO and surface plasmons opens a new route to enhance the UV emission and simultaneously suppress defects related visible emission.
In this work, we have demonstrated enhanced photoluminescence of ZnO nanorods by 1D and 2D metal gratings. 300 nm period gratings with different metals, i.e. Au, Ag, and Al were patterned on silicon (100) by laser interference lithography. ZnO nanorods were synthesized by hydrothermal method at 85 deg C on the patterned substrate. It is shown that the enhancement in luminescence strongly depends on metal materials and the height of ZnO nanorods. Preliminary results show the near band edge (NBE) emission at room temperature is enhanced by seven fold, which is attributed to the resonant coupling of spontaneous emission in ZnO with surface plasmons supported by the metallic nano-strucutres. The method presented in this work possesses advantages of low cost, large area periodic nano-patterns achievable and good controllability. It is believed that the luminescence enhancement will improve the efficiency of ZnO based optoelectronic devices.
9:00 AM - L9.86
Coherent Control of the Emission of an Organic Semiconductor Based Optical Microcavity
Eleonora Vella 1 Pascal Gregoire 1 Richard T. Grant 2 Richard Leonelli 1 Eric R. Bittner 3 David G. Lidzey 2 Carlos Silva 1
1Universite de Montreal Montreal Canada2University of Sheffield Sheffiels United Kingdom3University of Houston Houston USA
Show AbstractWe apply ultrafast optical probes to explore the nature of exciton polaritons in organic-semiconductor-based optical microcavities. Cavity polaritons are half-light half-matter quasi-particles arising when a photon confined in a cavity strongly interacts with an exciton. In practice this is obtained by incorporating a thin film of a semiconductor in a Fabry-Perot microcavity with an excitonic transition degenrate with the optical mode. The study of the dynamics of cavity polaritons in organic semiconductors is still at its infancy and this is remarkable because organic semiconductors represent a very promising frontier in this branch of physics: Their energy gap ranges from the visible to the near infrared and their oscillator strengths and excitonic bonding energies (sim;0.5 eV) are much higher than in inorganic semiconductors. This set of properties makes organic semiconductors in optical microcavities extremely promising for ground-breaking applications such as organic polariton lasers.
Here we present images of the far-field emission of a J-aggregates-based Fabry-Perot microcavity at 4 K. Such images were obtained by imaging the Fourier plane of an objective lens that collects the photons leaking out of the microcavity and they allow us to identify the energy dispersion of the polariton system. With the aim of clarifying the coherence properties of the polariton gas, we implemented an experiment of optical coherent control of the polariton state by resonantly exciting the polariton branches with a sequence of two femtosecond phase-locked pulses. The coherence state of the system can be controlled by cycling the relative phase of the two pulses at a given relative delay that is short with respect to the decoherence time. The resulting visibility is measured as a function of delay, thereby revealing coherence dynamics throughout the polariton dispersion curve.
9:00 AM - L9.87
Plasmonic Nanostructures for Silver and Copper Optically-Active Electrodes in Organic Photovoltaics
Divya Vijapurapu 1 Christopher Petoukhoff 1 Coleen Nemes 3 Gary Cheung 1 Deirdre M. O'Carroll 1 2
1Rutgers University Piscataway, New Jersey USA2Rutgers University Monmouth Junction USA3Marist College Poughkeepsie USA
Show AbstractA new method for trapping light in bulk-heterojunction (BHJ) solar cells is the incorporation of metallic nanostructures that support surface plasmons onto the electrodes of a device. A nanostructured metallic electrode can couple both photons and surface plasmons supported at the metal/semiconductor interface, where light may be converted into photocarriers. When applied to organic photovoltaics, this technique may allow considerable shrinkage of active layer thickness, while keeping effective optical absorption length constant.
However, for effective carrier collection the workfunction and electrode type (anode or cathode) must be carefully chosen. The results of theoretical calculations of open circuit voltage (Voc) establish that for inverted devices, the contacts that optimize Voc are copper (Cu), copper (II) oxide (CuO), and gold (Au), whereas silver (Ag) and aluminum (Al) are optimal for the conventional configuration.
In addition to this theoretical work, arrays of metal nanoparticles have been fabricated by thermally evaporating metal through nanoporous alumina masks to form nanostructured optically-active electrodes. Preliminary bright-field and dark-field spectroscopy measurements have been carried out on the arrays with and without the presence of a thin (<150 nm) film of poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM), to determine the enhancement in absorption and scattering of the solar spectrum. These measurements showed that uncoated silver nanostructures on a planar silver film enhanced extinction (sum of incident light absorption and scattering) by a factor of 2.3 relative to a planar silver film. In addition, dark-field scattering was enhanced by a factor of 0.7. Dark-field spectroscopic measurements of the silver nanoparticles on a planar silver film coated with P3HT:PCBM showed dark-field scattering enhancement of up to 7.5 relative to a planar coated silver film.
Current research has been focused on the fabrication of copper nanoparticle arrays on copper films so that enhancement in absorption and scattering can be determined and subsequently compared to the results for silver. So far, the challenges include the relatively fast oxidation of copper, the roughness of copper films when deposited via thermal evaporation, and the subsequent inability to distinguish nanoparticles from the rough particles that form the planar copper film. Possible solutions include the use of e-beam rather than thermal evaporation to achieve smoother films, so that deposited nanoparticles can be more easily distinguished. Ultimately, these measurements will establish which nanostructured material results in the largest absorption enhancement. This will determine their potential for use as “optically-active” metal electrodes in bulk-heterojunction solar cells. Successful developments in optically-active electrodes have the potential to push organic photovoltaics closer to competitive efficiencies.
9:00 AM - L9.88
Creation of Gold Core Copper Shell Nanoparticles with Tunable Plasmonic Characteristics and Unique Electronic Properties
Aparna Wadhwa 1 Anh Thi Ngoc Dao 1 Derrick Mott 1 Shinya Maenosono 1
1Japan Advanced Institute of Science and Technology Nomi Japan
Show AbstractIn recent years, bimetallic nanoparticles with complex structure (heterostructures) have received considerable attention because of their novel optical, electronic, magnetic and catalytic properties. These heterostructures offer the opportunity to tailor the properties through manipulation of the particle composition as well as structure. For example, the plasmonic properties of traditional gold nanoparticles can be manipulated or tuned by coating with an additional plasmonic metal such as copper. Such a particle structure is expected to display unique optical properties as a function of the thickness of the copper shell, however there is still considerable concern about the stability of the deposited copper in terms of oxidation. It was recently discovered however that in the case for gold coated by silver nanoparticles, the silver gained electron density from the gold, resulting in resistance to oxidation of the silver shell. In light of the observation, we also expect that the properties of copper can be modified by coating on gold nanoparticle cores. To test the idea, we created gold nanoparticles via the citrate reduction method and then deposited an additional copper shell through seed mediated growth. The technique allowed the copper shell thickness to be finely controlled. The resulting particles display tunable plasmonic properties and enhanced chemical state as a result of electronic transfer between the gold and copper in the core shell structure. The presentation relates our recent findings in the synthesis and characterization of gold coated by copper nanoparticles with controllable structure and plasmonic properties and will discuss the role of electron transfer in modifying the properties of the copper shell. The results are discussed in terms of synthesis technique, and characterization of the optical properties using techniques such as TEM, EDS, XRD, XPS, UV-Vis as well as others.
9:00 AM - L9.89
Enhanced Properties of Gold Core Copper Shell Nanoparticles
Aparna Wadhwa 1 Anh Thi Ngoc Dao 1 Derrick Mott 1 Shinya Maenosono 1
1Japan Advanced Institute of Science and Technology Nomi Japan
Show AbstractThe field of biomolecule detection has been rapidly advanced with the advent of gold nanoparticles (NP)s as sensing probes because these materials provide a highly sensitive mode of detection (plasmonic properties) and have a strong interaction with biomolecules through sulphur functionality. Gold NPs have been used as sensitive probes to detect molecules such as DNA, RNA, Protein, amino acids etc., enhancing our ability to identify and treat serious disease. Despite these advancements however, gold NPs still display some drawbacks, such as inability to manipulate the plasmonic properties of the material for a desired application. The synthesis of bimetallic NPs with sophisticated structures offers an opportunity to overcome this challenge by incorporating the properties of an additional metal to the NP structure. For example, gold coated by silver NPs have demonstrated remarkable oxidation resistance as a result of a unique electron transfer phenomenon that occurs at the interface of the two metals. Such an observation demonstrates the feasibility of integrating other metals with gold core NPs in the search for control of the plasmonic properties for these materials. To probe the plasmonic properties of this class of heterostructured NP system, we first created gold particles coated in copper. These particles displayed interesting electronic and plasmonic properties that arose as a result of electronic transfer between the gold and copper in the core shell structure. We characterized the electronic transfer using XPS analysis and studied the impact on the resulting particle stability and plasmonic properties. The results will be discussed in terms of the synthetic technique of the NPs, the structural and chemical characterization of the particles as well as the study on the electronic properties. The results provide insight into how to control the properties of plasmonic NP probes for sensing and diagnostics applications.
9:00 AM - L9.90
Luminescence from the Single Layer MoS2 and the Enhancement by Surface Plasmon Effect
Junzhuan Wang 1 Xiaoxu Wei 1 Hao Qiu 1 Yong Hu 2 Xinran Wang 1 Yi Shi 1
1Nanjing University Nanjing China2Nanjing University Nanjing China
Show AbstractMolybdenum disulphide (MoS2), a layered quasi-2 di-mensional (2d) chalcogenide material[1], is subject of intense research because of its electronic[2] and optical properties[3].The mono- and Bi-layer (1L or 2L, for short) MoS2 crystals are produced by micromechanical cleavage of bulk MoS2 90nm SiO2 characterized by Atomic Force Microscopy (AFM) and Raman scattering analysis . Photoluminescence was obtained from the 1L 2L-and bulk MoS2 at room temperature peaked around 630 and 680 nm originated from the well known A1 and B1 excitons.[3] Electroluminescence was realized by the Au/Ti Schottky contact with single layer MoS2 in the three terminal device with a 2mu;m channel.
Surface Plasmon effect was usually used to enhance the luminescence, we synthesized Gold and Silver nanoparticles with the resonant absorption peak around 514nm and 680nm which are corresponding to the excitation laser wavelength and the peak of the luminescence from the 1L MoS2, tentatively we obtained the maximum enhancement of the luminescence around 30 times due to the surface plasmon effect. Optimal enhancement condition is still under investigation. The latest results and the luminescence enhancement mechanism will be reported in the conference.
References:
[1] Qing Hua Wang, Kourosh Kalantar-Zadeh, Andras Kis, et.al. : Electronics and optoelectronics of two-dimensional transition metal dichalcogenides Nat. Nanotech. Vol 7 (2012) p 699
[2]Hao Qiu, Xinran Wang et. al. : Electrical characterization of back-gated bi-layer MoS2 field-effect transistors and the effect of ambient on their performances . Appl.Phys.lett. Vol 100 (2012) p 123104
[3] Andrea Splendiani, Liang Sun,et.al.: Emerging Photoluminescence in Monolayer MoS2 Nano.Lett. Vol 10 (2010) p 1271.
9:00 AM - L9.91
Strained GeSn/SiGeSn Double Heterostructure for Laser Applications
Stephan Wirths 1 Zoran Ikonic 2 Gregor Mussler 1 Toma Stoica 1 Uwe Breuer 3 Alessandro Benedetti 4 Stefano Chiussi 4 Jean-Michel Hartmann 5 Paul Harrison 2 Detlev Gruetzmacher 1 Siegfried Mantl 1 Dan Buca 1
1Forschungszentrum Juelich Aachen Germany2School of Electronic and Electrical Engineering, University of Leeds Leeds United Kingdom3Forschungszentrum Juelich Juelich Germany4Univ. de Vigo, Rua Maxwell s/n, Campus Universitario Vigo Spain5CEA, LETI Grenoble France
Show AbstractComplete photonic integrated circuits on Si will strongly benefit from the development of appropriate direct band-gap group IV semiconductors. It has been predicted that direct band-gap can be achieved in Ge with 2% tensile strain without a need for heavy n-type doping and relaxed GeSn alloys are direct gap for Sn concentrations of about 8-10%. However, the use of strained Ge(Sn) layers in optoelectronic applications like semiconductor lasers demands the development of suitable barrier layers. SiGeSn ternaries are ideal solutions for forming promising quantum-well structures since their band-gap and lattice constant can be tuned separately.
In this contribution we first present a group IV semiconductor laser design based on a SiGeSn/strained GeSn/SiGeSn double heterostructure. Their calculated electronic band structures indicate type I band alignment and conduction (Γ-valley) and valence (HH-band) band off-sets sufficient to sustain population inversion and hence make lasing possible. We show that lower strain levels are required to induce direct transition in low Sn content GeSn alloys. For the proposed quantum well laser structure, we discuss via optical net gain calculations the optimum conditions regarding tensile strain, Sn content and n-doping for a maximized laser gain. Especially, the role and the evolution of intra-valence band absorption vs. carrier injection concentration are addressed. Then, we demonstrate, using an industry compatible RP-CVD tool with showerhead technology, the epitaxial growth of such GeSn/SiGeSn double heterostructures on Ge virtual substrates on Si(100) as indicated by simulations. In this context, we present the single crystalline growth of high Sn content virtual substrates (Sn content ~14%) which (may) induce a direct-gap in Ge and GeSn binaries with lower Sn contents as well as to tensile strain direct gap Ge0.9Sn0.1 laser active layers. Aiming for an electrically pumped laser, we present the growth of highly n- and p-type doped SiGeSn layers to be used for carrier injection.
9:00 AM - L9.92
Quantum Surface Plasmonic Resonances of Metallic Nanoparticles: A Large-Scale Time-Dependent Orbital-Free Density Functional Theory Investigation
Hongping Xiang 1 Xu Zhang 1 Daniel Neuhauser 2 Gang Lu 1
1California State University Northridge Northridge USA2University of California,Los Angeles Los Angeles USA
Show AbstractThe plasmonic resonances of metallic nanoparticles in the quantum size regime are not well understood owing to their complex physical/chemical behavior and ensemble inhomogeneity. For example, there are contradictory experimental reports on whether the local surface plasmonic resonances are red-shifted or blue-shifted as the particle dimensions are reduced [1-2]. Theoretically, the classical electromagnetic theory cannot capture the quantum resonances, while the Kohn-Sham density functional theory (DFT) cannot deal with particle sizes more than 2 nm. Here we propose a time-dependent orbital-free density functional theory with a dynamic kinetic energy potential term and local pseudopotentials, which provide an exact description of frequency-dependent linear response of uniform electron gas. With this method, we can afford to study size-dependent surface plasmonic resonances of Na nanoparticles with diameters ranging from 0.7 nm to 10 nm. We find that the surface plasmonic excitation energy in fact depends on the particle size in a non-monotonic manner and three resonance modes could coexist. Other novel features of the quantum plasmonic behaviors will also be discussed.
[1] J. A. Scholl, A. L. Koh, J. A. Dionne, Nat. 483, 421 (2012)
[2] S. Peng, J. M. McMahon, G. C. Schatz, S. K. Gray, Y. Sun, Proc. Natl Acad. Sci. USA 107, 14530 (2010)
9:00 AM - L9.95
Time Resolved Study of Nonradiative Energy Transfer in Graphene Based Thin Films
Aydan Yeltik 1 Gokce Kucukayan 1 Somayye Fardindoost 1 2 Burak Guzelturk 1 Hilmi Volkan Demir 1 3
1Bilkent University Ankara Turkey2Sharif University of Technology Tehran Islamic Republic of Iran3Nanyang Technological University Singapore Singapore
Show AbstractGraphene has become a subject of great interest because of its unique electronic structure and optical properties [1]. Graphene has been also demonstrated to serve as a good exciton sink dominantly through Förster-type nonradiative energy transfer (NRET), e.g., from quantum dots (QDs) and dye molecules to graphene [2,3]. To date, high-quality epitaxial graphene has been widely studied. However, this requires epitaxial growth at elevated temperatures. On the other hand, solution-processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) offer attractive advantages that cannot be provided by the epitaxial graphene including ease of processing with low cost, large area coverage and tunable energy gap [4,5]. Therefore, NRET into GO and RGO, which may exhibit an exciton quenching range comparable to graphene [3,6,7], is particularly important to explore and understand the extend and feasible capacity of exciton sink as well as its required conditions.
NRET efficiency is strongly dependent on the distance between the exciton donor and acceptor pair [8]. To date, the efficiency of the exciton transfer into GO and RGO has not been studied in terms of the critical parameter of donor-acceptor separation distance. In this work, we studied systematically the exciton transfer distance in QD-GO and QD-RGO hybrid films using time-resolved measurements and modeling. These allowed us to analyze the excited state dynamics as a function of the donor-acceptor separation in detail. The time-resolved fluorescence spectroscopy results, reported here for the QD-GO and QD-RGO for the first time, confirm steady state fluorescence quenching. In our samples, thin QD coatings were achieved over uniform fully covered thin GO (1-2 ML) and thermally reduced thin RGO films. The NRET rates were found to be strongly dependent on the degree of reduction of the graphene based films. The separation of the QDs to the GO and also to the RGO was systematically controlled using dielectric thin films with thicknesses precisely varied by atomic layer deposition, demonstrating the spatial behavior of the resulting NRET. The NRET efficiencies were found to be around 97% and 89% for the closest separation of the QD-RGO pair and the QD-GO, respectively. These results reveal that the strong NRET from QDs into thin layer GO and RGO makes these solution-processable graphene-based thin films promising candidates to be used in excitonic light harvesting and detecting systems.
References:[1] K. S. Novoselov et al. Science 306, 666-9 (2004).[2] Z. Chen et al. ACS Nano 4, 2964-8 (2010).[3] L. Gaudreau et al. Nano Letters 13, 2030-2035 (2013).[4] K. P. Loh et al. Nature Chemistry 2, 1015-24 (2010).[5] S. Park et al. Nature Nanotechnology 4, 217-24 (2009).[6] J. Kim et al. Journal of the American Chemical Society 132, 260-7 (2010).[7] E. Morales-Narváez et al. Carbon 50, 2987-2993 (2012).[8] C. Kagan et al. Physical Review. B, Condensed Matter 54, 8633-8643 (1996).
9:00 AM - L9.96
Three Dimensional Chiral Plasmonic Nanostructures without Lithography
Bongjun Yeom 1 Huanan Zhang 1 Hui Zhang 2 Alexander Govorov 2 Nicholas Kotov 1
1University of Michigan Ann Arbor USA2Ohio University Athens USA
Show AbstractStrong chiral optical activity can be achieved for nanoscale structures with three dimensional (3D) tetrahedral or helical out-of-plane geometries. Their preparation on solid substrate was achieved in the past using complex lithographic processes capable of producing the 3D plasmonic architectures which have limitations in respect to both spectral window of chiral optical effects and the size of substrates. Here we present a facile route to 3D chiral plasmonic nanostructures (CPNs) with controllable optical activity in the visible range without using any lithographic process or chiral templates. Out-of-plane 3D geometry of the coatings is obtained using ZnO nanopillars grown perpendicularly to the substrate. The chirality of the nanopillars is achieved via two-steps depositions of gold carried out according to a specific protocol: (1) evaporation direction was inclined in respect to the plane of the substrate resulting in one-sided deposition of gold shells on nanopillars; and (2) substrate was rotated between the deposition steps by an angle α resulting in the symmetry breaking. Circular dichroism peaks of the prepared films were observed at 680 nm, i.e. in the plasmonic region of gold and had opposite signs for α = +/- 90 deg. Polarization rotation originates from the coupling of incoming light comparable in wavelength with the nanopillars. Theoretical calculations of the optical properties confirm the experimental observations. The described lithography-less technique to obtain 3D chiral plasmonic materials represents general platform to obtain optically active chiral films for metamaterials, optoelectronics, biomedical, and chiral catalysis.
9:00 AM - L9.97
Defect-Induced Resonances in Photonic Microdisk Resonators for Enhancement of Nanoparticle - Resonance Mode Interaction
Yasha Yi 1 2 M. Ostrowski 1 X. Duan 2
1University of Michigan Dearborn and Ann Arbor USA2MIT Cambridge USA
Show AbstractEnhancement of photonic resonator and nanoparticle interaction has been playing increasing important roles in next generation sensing, biomedical device and renewable energy fields. In this work, we demonstrate the applicability and universality of the phenomenological approach to the photonic resonance-nano particle interaction by focusing on resonances of a planar disk resonator interacting with a subwavelength, also planar, particle. In particular, we demonstrate that the response of this system to a TE-polarized excitation consists of two resonance peaks, both of which are shifted toward longer wavelengths from the initial single-disk resonance. This prediction, which is in contradiction with previous popular phenomenological model, is further confirmed by direct experimental observation of the peaks in the optical response of a silicon microdisk interacting with Si nanoparticles functionalized on its surface. Our results indicate that the assumption of direct coupling of the resonance modes of the resonator to the propagating modes of free space made is not sufficient to capture the essential mechanism of photonic resonance-particle interaction. A more appropriate model requires instead consideration of interaction between photonic resonance and modes of the particle, which are naturally coupled to the propagating modes. Our work will have a variety of applications for the performance enhancement of integrated optoelectronic materials and devices.
9:00 AM - L9.98
Improved Light Extraction Efficiency of Cerium-Doped Biomedical Imaging Scintillator by Monolayers of Periodic Arrays of Polystyrene Spheres
B. Liu 2 X. Duan 3 Yasha Yi 1 3
1University of Michigan Dearborn and Ann Arbor USA2Tongji University Shanghai China3MIT Cambridge USA
Show AbstractCerium-doped lutetium-yttrium oxyorthosilicate (LYSO) with advantages of high light output (~30 000 ph/MeV), good energy resolution (~10%), and short decay time (~40 ns) has become an excellent scintillator for the applications in medical imaging and wavelength conversion optoelectronic devices. In spite of the high internal quantum efficiency of LYSO, the light extraction efficiency is rather low due to its high refractive index (1.83), which leads to a small critical angle. The extraction efficiency from one side of the crystal-air interface is as low as 7.5%. In order to achieve a significant increase of light extraction, photonic crystals have been widely used in inorganic semiconductor light-emitting diodes (LEDs) and organic electroluminescence devices. Although the research on the enhancement light extraction efficiency in LEDs has attracted great attention, the application of photonic structures to the field of scintillators is scarcely reported. For practical purposes in scintillation detection systems, large-area patterned photonic crystals fabricated in low cost are highly desirable. Therefore, two-dimensional photonic crystals consisting of a monolayer of self-assembled hexagonal-close-packed (hcp) dielectric spheres prepared in a very economical and effective way holds a great promise. In this work, monolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the surface of cerium-doped lutetium-yttrium oxyorthosilicate scintillator to improve the light extraction efficiency. The enhancement of extraction efficiency up to 38% relative to the reference case without polystyrene spheres is achieved. Combining with the simulation for the transmission as well as its dispersion relation, detailed analysis of the effect of whispering gallery modes and diffraction on the extraction mechanism are given. As a result, the optimal diameter of 414 nm is obtained based on a trade-off between the transmission loss and the diffraction enhancement.
9:00 AM - L9.99
Enhancement of Light Extraction from Y3Al5O12:Ce3+ Ceramic Plate Phosphor Coated with TiO2 Nanohole Structure
Seong Woong Yoon 1 Hoo Keun Park 1 Hee Chang Yoon 1 Keyong Nam Lee 1 Young Rag Do 1
1Kookmin University Seoul Republic of Korea
Show AbstractThe conventional white light emitting diodes (WLEDs) combine a blue LED chip and a yellow [Y3Al5O12:Ce3+ (YAG:Ce)] powder phosphor coating with a silicone resin on the LED chip surface to obtain white emission. However, micro-size powder phosphor leads to limited conversion efficiency due to scattering and reflection loss of the emission. The transparent polycrystalline YAG:Ce ceramic plate phosphors (CPPs) have been used to achieve improved conversion efficiency. However, YAG:Ce CPP shows a low light extraction efficiency by waveguide effect and total internal reflection (TIR) because it is film-type phosphor.
In order to address this problem, a TiO2 nanohole structure as two-dimensional (2D) photonic crystal was introduced on the YAG:Ce CPP by a combination of e-beam evaporation, thermal evaporation, nanosphere lithography (NSL) and reactive ion etching (RIE) processes.
First, a TiO2 film was coated on the YAG:Ce CPP using E-beam evaporation process. Subsequently, the PS monolayers with various diameters (580, 720, 850, 960nm) were coated on the TiO2-coated CPP via a scooping transfer technique, forming the PS/TiO2/CPP structure. PS monolayer was thinned by RIE etching process to be used as deposition mask. A Cr mask layer for selective TiO2 etching was coated on thinned PS/TiO2/CPP by Thermal evaporator. After elimination of PS nanosphere, the Cr hole/TiO2/CPP was etched by RIE process. The remained Cr mask layer was eliminated by wet-etching process. Finally, the TiO2 nanohole-coated CPP was annealed at 450°C. The effects of the TiO2 nanohole structures with various lattice constants (580, 720, 850, 960nm) were investigated on the extraction efficiency of YAG:Ce CPP. The structural, morphological and optical properties of 2D TiO2 nanohole PCL-assisted YAG:Ce CPPs on top of a blue LED chip were investigated by scanning electron microscopy (SEM), photoluminescence (PL) measurements.
L7: Light Emitting Materials and Devices II
Session Chairs
Jaime Rivas
Koichi Okamoto
Thursday AM, December 05, 2013
Hynes, Level 2, Room 200
9:30 AM - *L7.01
Spontaneous Emission Faster than Stimulated Emission
Eli Yablonovitch 1 Ming C. Wu 1
1University of California, Berkeley Berkeley USA
Show AbstractFor almost 50 years, stimulated emission has been stronger and far more important than spontaneous emission. Indeed spontaneous emission has been looked down upon, as a weak effect. Now a new science of enhanced spontaneous emission is emerging, that will make spontaneous emission stronger and faster than any possible stimulated emission. This new science depends upon the use of nanoscale metallic optical elements, as antennas for spontaneous emission.
We call this antenna-enhanced effect “Spontaneous Hyper-Emission” (SHE). The overall increase in spontaneous emission rate can be up to 8 orders of magnitude, but will ultimately be limited the optical anomalous skin effect, which imposes extra Ohmic dissipation as quantum dots approach within nano-meters of metal surfaces. Currently we are using bare “naked” InGaAsP quantum dots, which have the remarkable property of radiating well, even without surface passivation, and even in direct contact with metallic optical antenna electrodes.
We will present the evidence for 35X spontaneous emission enhancement by an optical antenna.
10:00 AM - L7.02
Surface Plasmons at Metal-Organic Interfaces Embedded into DBR Resonators
Reinhard Scholz 1 Robert Brueckner 1 Alexander A. Zakhidov 2 Markas Sudzius 1 Hartmut Froeb 1 Vadim G. Lyssenko 1 Karl Leo 1 2
1Technische Universitamp;#228;t Dresden Dresden Germany2Fraunhofer COMEDD Dresden Germany
Show AbstractOptically pumped organic microcavities rely on the quite broad gain spectrum of excited molecules, allowing to investigate particular photonic resonances of these microcavities. At sufficient pump power, distinct spectral regions with a particularly large photonic density of states show stimulated emission and lasing even at room temperature.
The systems analyzed in the present contribution rely on a lambda;/2 layer of Alq3:DCM (2 wt.%) embedded between two distributed Bragg reflectors (DBRs). With an additional 40 nm Ag layer inside this microcavity, the single resonance is replaced by two Tamm states [1], and for one of them, the quality factor remains sufficiently high to show lasing, with a pump threshold only about a factor of 3 above a metal-free lambda;/2 microcavity [2].
According to the Bloch theorem, photolithographic structuring of the metal layer into a stripe pattern with period a induces periodicity in wave vector space with 2π/a, so that each Brillouin zone contains a replica of the original microcavity mode. The crossing points of the microcavity dispersion branches enhance the photonic density of states at the center and edge of each Brillouin zone, allowing for lasing along wave vectors of 0, π/a, and 2π/a [3]. The Tamm resonances from the metal-covered regions are quantized into standing waves with discrete energies. Superimposed to the microcavity and Tamm resonances, the periodically patterned Ag stripes induce seemingly linear dispersion branches. These arise from Bragg scattering of surface plasmons up to very high orders, allowing eventually to detect these plasmonic resonances inside the air light cone [3].
Transfer matrix calculations of the multilayer system reveal the dispersion relation of the microcavity resonance, the Tamm states and the surface plasmons together with their envelopes across organic gain medium, metal layer, and DBR region. The plasmonic dispersion branches do not correspond anymore to the well known surface plasmon at a single interface, but they become merely a property of the entire arrangement with particular continuity conditions of electric field and dielectric displacement at each interface.
[1] R. Brückner, M. Sudzius, S. I. Hintschich, H. Fröb, V. G. Lyssenko, and K. Leo, Phys. Rev. B 83, 033405 (2011).
[2] R. Brückner, A. Mischok, A. a. Zakhidov, S. I. Hintschich, H. Fröb, V. G. Lyssenko, M. A Kaliteevski, and K. Leo, submitted (2013).
[3] R. Brückner, A. a. Zakhidov, R. Scholz, M. Sudzius, S. I. Hintschich, H. Fröb, V. G. Lyssenko, and K. Leo, Nature Photonics 6, 322 (2012).
10:15 AM - L7.03
Tailoring the Spontaneous Emission from Silicon Nanocrystals with Surface Plasmons
Julie Goffard 1 2 Davy Gerard 1 Patrice Miska 2 Anne-Laure Baudrion 1 Michel Vergnat 2 Jerome Plain 1
1Technical University of Troyes Troyes France2Jean Lamour Institute Nancy France
Show AbstractThe use of silicon nanocrystals (SiNC) in optoelectronic devices has risen from a decade thanks to the discovery of photoluminescence in porous silicon in 1991 [1]. However SiNCs exhibit a low quantum yield, which prevent from currently using them in optoelectronic devices. This problem can be bypassed thanks to the use of localized surface plasmons (LSP). Indeed LSPs can modify emitters&’ photoluminescence by changing the optical local density of states and/or increasing the local excitation field. Numerous studies have been realized with different emitters but the study of LSP coupled with SiNC is scarce. Seminal studies by Biteen and coworkers [2,3] have paved the way for increasing SiNCs&’ performances with LSPs. In these preliminary works only the SiNCs&’ emission wavelength was coupled to LSPs.
In this work, we present a study where LSPs resonances are coupled simultaneously with the absorption and emission wavelengths of SiNCs. Our original fabrication method gives us the control of all the geometrical parameters that modify the SiNCs-LSPs coupling. The use of nanorods with different shapes and metals allows us to have two plasmon modes. One is located at the SiNC&’s absorption wavelength and the other is located at the SiNC&’s emission wavelength. The SiNC&’s photoluminescence enhancement is thus due to two physical phenomena. To understand these phenomena, we study the influence on SiNC&’s photoluminescence intensity, polarization and spatial redirection. We also extract the SiNCs&’ radiative quantum yield enhancement in presence of these rods.
[1] A. G. Cullis, L. T. Canham, Nature 1991, 353, 335-338.
[2] J. S. Biteen, D. Pacifici, N. S. Lewis, H. A. Atwater, Nano Lett. 2005, 5, 1768-1773.
[3] J. S. Biteen, N. S. Lewis, H. A. Atwater, H. Mertens, A. Polman, Appl. Phys. Lett. 2006, 88, 131109.
10:30 AM - L7.04
Au-CdTe Nanohybrids: Experimental Evidence of the Plasmonic Dicke Effect
Miguel Comesana-Hermo 1 Pierre Fauche 1 Alexis Fradon 1 Renaud Vallee 1 Serge Ravaine 1
1CNRS-Centre de Recherche Paul Pascal Pessac France
Show AbstractIt has been postulated that for an ensemble of dipoles situated at the surface of a plasmonic nanoparticle (NP) the interaction between emitters is of plasmonic character, rather than radiative, leading to the formation of collective states known as “superradiant modes”.[1] These results are an extension of the previous work by Dicke, in which he postulated the existence of such states for an ensemble of dipoles confined in a volume smaller than the radiation wavelength.[2] To the best of our knowledge, there has been no experimental demonstration of the plasmon-mediated superradiance near metal nanoparticles, this being a consequence of the difficulty to create a system in which the number of dipoles per plasmonic core and the distance between them are precisely controlled.
In our work, we have synthesized Au-CdTe nanohybrids as model system. This composite has been created attaching water-soluble CdTe quantum dots (QDs) at the surface of Au nanoparticles, while the distance between the emitters and the plasmonic core has been finely controlled using polyelectrolytes or silica as spacers. Moreover, the concentration of CdTe QDs in solution has been varied to obtain different populations of these NPs attached at the surface of the Au core. Time-resolved fluorescence spectroscopy has been used to study the light-matter interactions within the system, both in solution and in single particle measurements. This will allow us to determine the collective emission rates as a function of wavelength, concentration of quantum dots and QD-NP distance to finally compare the experimental data with the theoretical predictions.
[1] V. N. Pustovit, T. V. Shahbazyan Phys. Rev. Lett., 102 (2009), 077401.
[2] R. H. Dicke, Phys. Rev., 93 (1954), 99.
10:45 AM - L7.05
Coupling and Fluorescent Enhancement of Semiconductor Nanoemitters on the Tips of Plasmonic Nanoantennas
Chao Liu 1 Pengfei Zhang 2 Kwanoh Kim 1 James H. Werner 2 Donglei Fan 1
1The University of Texas at Austin Austin USA2Los Alamos National Laboratory Los Alamos USA
Show AbstractSurface plasmon (SP), due to collective oscillation of conduction-band electrons in noble metals, can be confined within a sub-optical-wavelength dimension and propagate at the interface between a conductor and a dielectric medium. It has received great attention due to the potential applications in ultrafast optical computation and communication. The integration of nanoemitters with plasmon waveguides for enhanced optical devices is of particular research interest. Great efforts are focused on assembling such devices, but it remains extremely difficult.
In this work, we used electric tweezers - our recently invented nanomanipulation technique - to assemble large ordered arrays of tip enhanced QD-plasmonic-nanoantenna hybrid device. By applying an optimized AC field on our designed microelectrode chip, randomly dispersed plasmonic nanowires can be readily aligned and self-assembled with essentially uniform interspacing on the top of microelectrodes. Then, QDs which were dispersed in this suspension were swiftly attracted to the tips of plasmonic nanowires. By coating a variable thickness silica layer on plasmonic nanowires, the fluorescent intensity and life time of QDs as a function of thickness were systematically investigated when QDs attached to the tips of the modified plasmonic nanowires. This work may inspire a new general paradigm for assembling large order arrays of tip enhanced QD-plasmonic nanoantenna hybrid device.
11:30 AM - *L7.06
Material, Order and Function in Self-Assembled Photonic Structures
Cefe Lopez 1
1CSIC Madrid Spain
Show AbstractAdvanced photonic materials are essentially based on structures sculpted to feature sizes comparable to or shorter than the wavelength of light. Even single-material structures may present interesting features such as light diffraction and photonic band-gaps; diffusion and localization, etc.
When several components are incorporated the properties expand and offer new possibilities. This is the case, for example, when passive dielectrics are mixed with chromophores or metals are combined with dielectrics. Beside the choice of materials the interplay between order and disorder occupies a central position in designing functions.
These structures can be turned into thermal switches, humidity sensors, ordinary or random lasers, etc. that can be prepared by inexpensive selfassembly and templating techniques. They most often involve water at some stage which imparts interesting properties whose nanoscale study links optics with mechanical properties. Some materials aspects presented by opals at micrometer scale can help understand seemingly as unrelated systems as wet granular materials. [1]
Lasers created upon these photonic structures can benefit from the possibilities offered by FRET phenomena such as in DNA-supported dyes. Such a strategy improves the performance of single dyes and expands their potential through tuneable coupling.[2]
Additional laser functionalities are enabled if beside the material and morphology it is possible to engineer the pumping: addressing selected modes and mode locking,[3] mode portation, switching, amplification, [4] as well as non-local collective processes.[5]
References
[1] Gallego-Goacute;mez, F. et al., Nano Letters, 12, 4920 (2012).
[2] Ibisate, M et al., Adv. Opt. Mater.in press (2013)
[3] Leonetti, et al., Nature Photonics, 5, 615 (2011).
[4] Leonetti, M et al., Nature Communications, 4, 1740 (2013).
[5] Leonetti, M et al., Light: Science & Applications, in press (2013).
12:00 PM - L7.07
Multilayered Metamaterial Based on Metal-Dielectric for Nanoscale Emitters
Sangram K Pradhan 1 R. Mundle 1 Q. Yang 1 J. R. Skuza 1 B. Xiao 1 Aswini K Pradhan 1
1Norfolk State University Norfolk, Virginia USA
Show AbstractWe have fabricated a multilayered metamaterial consisting of alternate noble metal (Ag or Au) and dielectrics (TiO2, ZnO or Silicone) which has capability to operate in the visible region. Optical properties and both real and imaginary dielectric permittivity were measured. We demonstrated the tunability of the multilayer films which depend of the nature of the dielectrics as well as their layer thickness. The crossover wavelengths were measured using ellipsometry technique for each set of multilayer films in order to quantitatively determine the tunability (basically the dependence of crossover wavelength from positive to negative permittivity), which is found to match with our simulations. The absolute transmission reduces with increasing number of multilayer pairs due to metal absorption. We have optimized the system to fabricate grating structure for designing nanoscale emitters for light emission control. The detail results will be presented.
12:15 PM - L7.08
Control of Photonic Mode Density inside a Core of a Multi-Layered Dielectric Sphere
Hiroki Shibata 1 Kenji Imakita 1 Minoru Fujii 1
1Kobe University Kobe Japan
Show AbstractThree dimensional (3D) photonic crystals, defined by 3D periodic dielectric structures whose periodicity matches the wavelength of photons, have attracted much attention due to their potential applications as ultra-low threshold lasers, single photon sources, and nonlinear photonics devices. In this work, we report a new kind of a 3D photonic crystal structure, which consists of a sphere coated by multi-layers. When the optical thickness of each layer coincides with a quarter wavelength, the stack works as a Bragg mirror and can confine photons three-dimensionally inside the core. Due to the complete point symmetry about the center of the sphere, a high quality factor and a wide photonic band gap can be obtained. We investigate both experimentally and theoretically the optical properties of a multi-layered sphere.
Theoretically, we calculate the radiative decay rate of an oscillating dipole placed in a core of a multi-layered sphere.[1] The periodic layers are assumed to be yttrium oxide (Y2O3) and silicon oxide (SiO2), possessing refractive indices of 1.91 and 1.45, respectively. The thickness of each layer is fixed to be a quarter wavelength. We obtained a sharp resonant peak of radiative decay rate and a broad photonic band gap beside them. The quality factor of the resonant peak increases exponentially with increasing the number of layers.
Experimentally, we prepare three layered sphere by using chemical solution processes in three steps. The first one is the preparation of core spheres of cerium-ion doped Y2O3 by a homogeneous precipitation method. The second one is the coating of SiO2 layer on the surface of core particles by a sol-gel method. The final one is the coating of Y2O3 layer on the surface of the SiO2-coated Y2O3 particles by a homogeneous precipitation method. The thickness of each layer can be estimated from the difference between the size distributions in each step and each layer thickness almost coincides with a quarter optical wavelength. We measured the photoluminescence properties of these particles. By coating Y2O3 layer on the surface of SiO2-coated Y2O3 particles, spectral width of luminescence peak became narrow and the modification of PL spectra well coincides with the calculated result. This result suggests that the photonic mode density can be controlled by using multi-layered structure. [1] K. Imakita, et al., Opt. Express. 21, 9 (2013).
12:30 PM - L7.09
High-Performance Inverted Top-Emitting Green Electrophosphorescent Organic Light-Emitting Diodes with a Modified Top Ag Anode
Ehsan Najafabadi 1 Keith A. Knauer 1 Wojciech Haske 1 Bernard Kippelen 1
1Georgia Institute of Technology Atlanta USA
Show AbstractGreen electrophosphorescent inverted top-emitting organic light-emitting diodes with a
Ag/1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) anode are demonstrated.
A high current efficacy of 124.7 cd/A is achieved at a luminance of 100 cd/m2 when an optical outcoupling layer of N,N;-di-[(1-naphthyl)-N,N;-diphenyl]-1,1'-biphenyl-4,4'-diamine (alpha-NPD) is deposited on the anode. The devices have a low turn-on voltage of 3.0 V and exhibit low current efficacy roll-off through luminance values up to 10,000 cd/m2. The angle dependent spectra show deviation from Lambertian emission and color change with viewing angle. Hole-dominated devices with Ag/HAT-CN electrodes show current densities up to three orders of magnitude higher than devices without HAT-CN.
12:45 PM - L7.10
Plasmonic Hybrids Based on Au/SiO2 and Conjugated Polymer with Tunable Photoluminescence Output
Zhongwei Liu 1 2 Xuyi Wang 2 Mircea Cotlet 1
1Brookhaven National Lab Upton USA2Stony Brook University Stony Brook USA
Show AbstractPlasmonic hybrid materials incorporating metal nanoparticles and semiconducting materials such as conjugated polymers and colloidal quantum dots have attracted intense interests for applications such as optoelectronics and biosensing. Engineering of such hybrids via simple and cost-effective self-assembly methods is sought in order to control the plasmon-exciton interaction between components towards improved performance and depending on the foreseen application.
Here we demonstrate self-assembly of core/shell Au/SiO2 nanoparticles with a cationic conjugated polymer (polythiophene derivative) onto plasmonic hybrids with tunable photoluminescence output. By varying the SiO2 shell thickness in the rage 5-30nm and for Au nanoparticles of 50nm core size, we demonstrate the ability to tune the conjugated polymer photoluminescence from regimes of efficient PL quenching to PL enhancement of up to five fold. We do this by using alternating laser single particle confocal photoluminescence spectroscopy by exciting outside and onto the Au surface plasmon resonance. The utility of the proposed hybrids for optoelectronic applications is demonstrated by coating the Au/SiO2/conjugated polymer plasmonic hybrids with fullerene acceptor molecules for which we observe plasmon assisted enhancement in the charge transfer rate between polymer and fullerene.