Bryan D. Huey University of Connecticut
Oleg V. Kolosov Lancaster University
Seungbum Hong Argonne National Laboratory
Hyunjung Shin Kookmin University
VV1: Molecular Studies
Monday AM, November 29, 2010
Fairfax A (Sheraton)
9:30 AM - **VV1.1
Touching Molecules at Forces Less than a Single Atomic Bond.
Stephen Minne 1 , C. Su 1 , S. Hu 1 , N. Erina 1 , J. Kindt 1 , A. Slade 1 Show Abstract
1 AFM Unit, Bruker Corporation, Goleta, California, United States
The AFM has long been recognized for its ability to both image surfaces and determine mechanical and electrical properties at the nanoscale. However, until recently, the combination of these capabilities was often a compromise between achievable imaging rate, quality of material property data, and sample compatibility requirements for electrical characterization.In this talk we present a new way to control the atomic force microscope and acquire simultaneous quantitative mechanical properties, and electrical conductivity maps, at the nanometer scale. In this new technology, the instantaneous interaction force during tapping is used to control tip-surface interaction while imaging. The force control accuracy allows imaging at 10 pN interaction force, without drift, in ambient or fluid. More importantly, the measurement records full interaction force curve and calculate modulus, deformation (hardness), adhesion and energy dissipation concurrent with the topographic imaging process. New advances in this technology allow this technique to be applied to electrical and electrochemical modes of SPM operation. In the newly developed electrical modes Peakforce Tapping-conductive atomic force microscopy (PFT-CAFM) is used to study LiMn1/3Ni1/3Co1/3O2 cathode composite. Many other examples in nanotechnology and polymers will also be given.
10:00 AM - VV1.2
Force Spectroscopy Study in Liquids by Frequency Modulation AFM Toward Local Charge Mapping at Solid/liquid Interface.
Ken-ichi Umeda 1 , Yoshiki Hirata 3 , Noriaki Oyabu 1 , Kei Kobayashi 2 , Matsushige Kazumi 1 , Hirofumi Yamada 1 Show Abstract
1 Department of Electronic Science and Engineering, Kyoto University, Kyoto Japan, 3 Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba Japan, 2 Innovative Collaboration Center, Kyoto University, Kyoto Japan
We recently succeeded in development of a frequency modulation atomic force microscope (FM-AFM) operating in liquids with atomic/molecular resolution by reducing the noise in the optical beam deflection sensor and by oscillating a cantilever at a small amplitude. We also visualized local hydration structures at solid-liquid interfaces by the two- or three-dimensional force mapping technique using the FM-AFM. The structures and functions of biomolecules are closely related not only to the hydration structures but also to the surface charge distributions. However, in physiological environments, the surface charge is screened by the surrounding counter ions in the solution, forming an electric double layer. Therefore, the electrostatic interaction between the probe tip and the surface charge is not as simple as that in vacuum, which prevents us from measuring a surface charge distribution in liquids at nanometer scale. As a first step toward local charge mapping at solid-liquid interfaces by FM-AFM, we studied the dynamics of the cantilevers in liquid environments when they were excited electrostatically by applying a modulating bias voltage between the cantilever and sample surface. We found that the cantilever oscillation was mainly induced by the surface stress modulation in the frequency range lower than 100 kHz. On the other hand, the cantilever was excited by the electrostatic force in the high frequency range. We also found that the oscillation amplitude of the cantilever driven at the high frequency did not show steep increase when the tip was brought in a close proximity to the sample surface in polar solvents. We consider that it is difficult to perform local charge mapping by detection of the oscillation amplitude driven by the electrostatic force.As a second step, we are currently studying the electric double layer force by FM-AFM. The electric double layer force, which is also known as osmotic pressure, is a force induced by overlap of the electric double layers of the tip and the sample. Detection of the electric double layer force has been demonstrated by the use of the conventional AFM technique with a very soft cantilever. However, the jump-to-contact induced by the adhesion force prevents an accurate measurement and limits the lateral resolution. In this study, we employed FM-AFM using a very stiff cantilever with a spring constant of 40 N/m. The cantilever was excited by the photothermal method so that we can obtain the ideal frequency characteristics, which is important for accurate force measurements. We found that the frequency shift of the cantilever includes that induced by the electric double layer force. We also found that the method is promising for two- or three-dimensional mapping of local charge at a solid/liquid interface.
10:15 AM - VV1.3
Low Frequency Dielectrophoretic Force Microscopy (LF-DEPFM): A Novel Non-contact AFM Mode for Surface Topography and Charge Imaging in Aqueous Solution.
Erik Hsiao Liao 1 , David Marchand 1 , Seong Kim 1 Show Abstract
1 Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
We developed a novel non-contact AFM mode for imaging in aqueous solution called low frequency dielectrophoretic force microscopy (LF-DEPFM). In this mode, dielectrophoretic force is generated at low frequencies (typically, ω <6 kHz) and dynamic response of the cantilever vibration and perturbation due to tip-surface interactions are monitored. The simultaneous monitoring of the second harmonic (2ω) and first harmonic (1ω) vibrations allow imaging surface topography and charge in non-contact mode in aqueous solution. The dielectrophoretic driving force was modeled with a simplified theoretical model. Various model surfaces and samples were tested to test the advantages and spatial resolutions of LF-DEPFM. These include self-assembled monolayers (SAMs) with COOH, CH3, and NH2 functional groups on gold, polyelectrolytes, and oxide surfaces and nanoparticles. The effects of pH and ionic strength of the aqueous solution were also tested to find operational limitations.
11:00 AM - **VV1.4
Catalytic Model Systems Studied by High-resolution, Video-rate Scanning Tunneling Microscopy.
Flemming Besenbacher 1 Show Abstract
1 Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus Denmark
Developing renewable, sustainable and green energy resources and securing the environment by reducing the emission pollutants are two of the largest challenges for the human civilization within the next 50 years. Besides the well known energy resources that power the world today, petroleum, coal, and natural gas, active research and development is done exploring alternative energy resources such as solar, biomass, wind, and hydrogen. Research and innovation within the area of the rapidly expanding field of nanoscience and nanotechnology, multi-disciplinary by nature involving physics, chemistry, biology, molecular biology, is mandatory to make the vision of a clean society and our vision of plentiful, low cost sustainable energy, a reality.For decades single-crystal surfaces have been studied under ultra-high vacuum (UHV) conditions as model systems for elementary surface processes. This “surface science approach” has contri-buted substantially to our understanding of the processes involved in especially catalysis. In this talk I will show how STM can reveal fundamental processes in relation to catalysis, and how we can extract quantitative information on surface diffusion of adatoms and molecules. We use time-resolved, high-resolution STM images/movies to understand diffusion of vacancies, interstitials and molecules, e.g. water molecules on oxide surfaces, sintering and diffusion of nanoclusters on oxide surfaces, diffusion of intermediate species, and to identify active sites and to determine new nanostructures with novel catalytic properties (see www.phys.au.dk/spm) [1-9]. The atomic-scale information obtained may even lead to the design of new and improved catalysts in certain cases .References1.F. Besenbacher, Reports on Progress in Physics 59, 1737 (1996)2. T. Linderoth et al. Phys. Rev. Lett. 78, 4978 (1997) 3. S. Horch et al., Nature 398, 1344 (1999)4.S. Wendt et al., Physical Review Letters 96, 066107 (2006)5. S. Wendt et al. Science 320, 1755 (2008) 6.D. Matthey, et al., Science 315, 1692 (2007) . 7. J. V. Lauritsen et al., J. Catal. 197 1-5 (2001)8. J. Kibsgaard et al, Journal of the American Chemical Society, 128, 13950 (2006).9. J. V. Lauitsen et al., Nature Nanotechnology, 2, 53 (2007)10.F. Besenbacher et al., Science 279, 1913 (1998).
11:30 AM - VV1.5
Crystallographic Processing of Scanning Probe Microscopy Images of Molecular 2D Periodic Monolayer Arrays.
Peter Moeck 1 , Jack Straton 1 , Pavel Placinda 1 , Taylor Bilyeu 1 , Marius Toader 2 , Michael Hietschold 2 , Norbert Koch 3 , Juergen Rabe 3 Show Abstract
1 Physics, Portland State University, Portland, Oregon, United States, 2 Physics, University of Technology, Chemnitz Germany, 3 Physics, Humboldt University, Berlin Germany
Traditional scanning probe microscope (SPM) images of 2D periodic arrays are processed crystallographically in order to quantify their deviations from the 17 plane groups. This information is then used to remove from the SPM image all kinds of geometric distortions that are due to the “less than perfect” imaging process. The combined effects of these distortions result in a point spread function that gives a quantitative measure of the microscope’s performance for a certain set of experimental parameters. On the basis of highly symmetric “calibration samples”, the point spread function of the microscope can be extracted and utilized for the correction of SPM images of unknowns that were recorded under essentially the same experimental conditions. A blunt scanning tunneling microscopy (STM) tip that consists of multiple mini-tips with electron orbital dimensions is symmetrized on the basis of prior knowledge on the plane symmetry of a 2D periodic array (P. Moeck et al., AIP Conf. Proc. 1173 (2009) 294). The 46 black-white groups are the basis of the extension of “classical” crystallographic image processing to images that were recorded with non-traditional SPMs, e.g. spin-polarized STMs and critical dimension SPMs.The removal of the effects of the point spread function of the microscope from the experimental data and the symmetrization of blunt STM tips both work because crystallographic image processing finds for each plane (or black-white) group the positions in Fourier space about which the respective set of symmetries is the least broken. Then it declares these positions as the crystallographic origin and symmetrizes the Fourier transform coefficients of the image intensity to this origin by averaging over all symmetry equivalent coefficients. A Fourier transform of the symmetrized Fourier coefficients back into direct space leads subsequently to the symmetry enforced SPM image with all geometric distortions removed. “Essentially independent” STM images that a blunt scanning probe tip recorded are all symmetrized (and shifted) to the same crystallographic origin. A beneficial byproduct is then the enhancement of the signal to noise ratio. Interference effects between the tunneling currents of the individual mini-tips (that make up the blunt tip) are symmetrized as well. Our analyses show, however, that systematic errors that may be associated with such interference effects are typically small.
11:45 AM - VV1.6
Molecular Resolution Imaging at Ambient Conditions with AFM Operating in AM Mode.
Andrey Krayev 1 , Sergey Bashkirov 1 , Victor Baukov 1 , Alexey Belyaev 1 , Vasily Gavrilyuk 1 , Dmitry Evpolv 1 , Dmitry Eliseev 1 , Vladimir Zhizhimontov 1 , Mikhail Zhdanov 1 , Vladimir Ivanov 1 , Sergey Katsur 1 , Sergey Kostromin 1 , Mikhail Savvateev 1 , Alexey Temiryazev 1 , Mikhail Trusov 1 , Yuri Turlapov 1 , Alexander Yagovkin 1 , Alexander Yalovenko 1 , Sergey Saunin 1 Show Abstract
1 , AIST-NT Inc, Novato, California, United States
Data will be presented on high resolution AFM imaging of SAMs of pristine linear alkanes, their mixtures and SAMs of Azelaic and Trimesic acids on HOPG in ambient conditions and in liquid. True molecular resolution has been achieved on SAMs of Trimesic acid in air. Advantages of the use of AFM vs STM for the characterization of molecular layers will be discussed.
12:00 PM - **VV1.7
Atomic Resolution Imaging of Single Molecules with Noncontact Atomic Force Microscopy.
Fabian Mohn 1 , Leo Gross 1 , Nikolaj Moll 1 , Jascha Repp 2 1 , Gerhard Meyer 1 Show Abstract
1 , IBM Research - Zurich, Rueschlikon Switzerland, 2 Institute of Experimental and Applied Physics, University of Regensburg, Regensburg Germany
It was recently shown that atomic resolution can be achieved in noncontact AFM imaging of single organic admolecules by functionalizing the AFM tip with a suitable atomic termination [Gross et al., Science 325,, 1110 (2009)]. In this contribution, the basic principles of the technique are discussed and measurements are presented that further elucidate the mechanism underlying atomic-resolution molecular imaging and emphasize the usefulness of this new technique. In particular, we show atomically resolved force map measurements on pentacene and PTCDA molecules adsorbed on Cu(111) and ultrathin NaCl films. PTCDA contains oxygen heteroatoms and adsorbs in a nonplanar geometry, making it an excellent example for investigating the particular contributions of geometry and chemical composition to the contrast observed in the AFM images. Furthermore, we present atomically resolved AFM images of a beforehand unknown organic molecule, which - in combination with DFT calculations and analysis by mass spectroscopy and nuclear magnetic resonance - enabled the unambiguous determination of the chemical structure of the molecule to be cephalandole A.
12:30 PM - VV1.8
Surface Electrochemical Potential Mapping of Graphene on SiC(0001).
Shuaihua Ji 1 , James B. Hannon 1 , Rudolf Tromp 1 , Arthur W. Ellis 1 , Mark C. Reuter 1 , Frances M. Ross 1 Show Abstract
1 , IBM Research Division, T. J. Watson Reseach Center, Yorktown Heights, New York, United States
Scanning tunneling potentiometry (STP) uses the tip of a scanning tunneling microscope (STM) to simultaneously measure the topography and the local electrochemical potential of a sample. By applying a voltage between two stationary probes in a multiprobe STM and following the potential drop across the surface with a third scanning tip, STP can yield a detailed picture of electron transport within a conducting surface layer. We have employed this technique to study the local transport properties of graphene on the SiC(0001) surface, important both for understanding the physics of electron transport across terraces and steps, and for developing device applications of epitaxial graphene. Samples were grown in a UHV low energy electron microscope (LEEM) by annealing SiC above 1300oC in a background pressure of disilane. The decomposition of SiC under these circumstances creates large graphene domains whose thickness (in the 1-2 ML range) can be determined directly from the LEEM contrast. After growth, samples were transferred to a UHV low temperature multiprobe system, and the areas that had been imaged in the LEEM were located. The defects and step geometry were characterized by STM, and the local topography and the electrochemical potential of the sample were derived from STP at liquid nitrogen temperature. LEEM provided the graphene thickness, which can not be deduced directly from STM scans. The electron scattering on terraces can be determined from the gradient in electrochemical potential, while surface topography of the substrate and changes in graphene thickness have a more complex effect on the scattering. We will describe analysis of these results in terms of electron transport at the local level through the graphene sheet.
VV2: New Probes, Optics and SPM
Monday PM, November 29, 2010
Fairfax A (Sheraton)
2:30 PM - **VV2.1
High Resolution Field Effect Sensing of Ferroelectric Charges.
Hyoungsoo Ko 1 2 , Kyunghee Ryu 3 , Hongsik Park 1 4 , Chulmin Park 1 2 , Daeyoung Jeon 1 5 , Yong Kwan Kim 1 2 , Juhwan Jung 1 2 , Dong-Ki Min 1 2 , Yunseok Kim 6 , Ho Nyung Lee 7 , Yoondong Park 2 , Hyunjung Shin 3 , Seungbum Hong 1 8 Show Abstract
1 Semiconductor Devices Laboratory, Samsung Advanced Institute of Technology, Yongin Korea (the Republic of), 2 Semiconductor Devices Laboratory, Samsung Electronics, Kyunggi-do Korea (the Republic of), 3 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 4 Division of Engineering, Brown University, Providence, Rhode Island, United States, 5 School of Electrical Engineering, Korea University, Seoul Korea (the Republic of), 6 Microstructure Physics, Max Planck Institute, Halle Germany, 7 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 8 Materials Science Division, Argonne National Laboratory, Lemont, Illinois, United States
Nanoscale manipulation of surface charges and their ultrafast imaging are emerging techniques for understanding local electronic behaviors of polar materials and for advancing information storage devices. Here we present scanning resistive probe microscopy (SRPM) that can directly image surface charges on a length scale of 25 nm and a time scale of less than 125 µs. Based on the calculation of net surface charges in a 25 nm diameter ferroelectric domain, we could estimate the charge density resolution to be as low as 1/20 of single electron per square nanometer at room temperature.
3:00 PM - VV2.2
High Resolution Electrostatic Force Microscopy with Coaxial Probes.
Keith Brown 1 , Jesse Berezovsky 1 2 , Robert Westervelt 1 3 Show Abstract
1 School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Physics, Case Western Reserve University, Cleveland, Ohio, United States, 3 Department of Physics, Harvard University, Cambridge, Massachusetts, United States
Electrostatic force microscopy (EFM), based on the interaction between a conducting atomic force microscopy (AFM) probe and a sample, is a powerful tool that has been used to study electrical properties of many materials at the nanoscale. Conventional EFM is done with an unshielded probe that has spatial resolution that is limited by the long range nature of the monopolar electrostatic interaction, thus typical EFM measurements include contributions from the cantilever and entire probe. We present shielded EFM probes that have a ground shield covering the probe down to exposed nanoscale coaxial electrodes at the tip. In addition to blocking long range interactions, the shielded probe suppresses the monopole component of the electric field at the tip and creates an electric field that is dipolar in character. The shorter range dipolar field allows for higher spatial resolution imaging. We have previously used electric field confining shielded probes to manipulate microscale objects using dielectrophoresis (DEP) and here we use DEP to model the forces and give a prediction for the improvement in resolution. We describe the nanofabrication of coaxial EFM probes and present experiments comparing the spatial resolution of coaxial and unshielded EFM probes.  Keith A. Brown, Jonathan A. Aguilar, and R. M. Westervelt, “Coaxial atomic force microscope tweezers,” Applied Physics Letters 96 (2010).
3:15 PM - VV2.3
Microfabrication of the combined AFM-SECM Sensors utilizing Focused Ion Beam and isotropic Inductively Coupled Plasma-Reactive Ion Etching.
Amra Avdic 1 , Alois Lugstein 1 , Ming Wu 3 , Bernhard Gollas 2 3 , Ilya Pobelov 4 , Thomas Wandlowski 4 , Emmerich Bertagnolli 1 Show Abstract
1 Institute of Solid State Electronics,, Vienna University of Technology, Vienna Austria, 3 , Competence Centre for Electrochemical Surface Technology, Wiener Neustadt Austria, 2 Institute for Chemistry and Technology of Materials, Graz University of Technology, Graz Austria, 4 Department of Chemistry and Biochemistry, University of Bern, Bern Switzerland
Combined atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) has emerged as a promising technique for high resolution simultaneous topographical and electrochemical imaging. By now two main approaches have been developed. The first one is the so called integrated AFM-SECM tip with a frame shaped electrode integrated at a defined distance to the apex of the tip, thereby controlling the distance to the sample surface. The other one is a conductive AFM probe, completely insulated except for a small part at the apex of the tip. The advantages of the second approach are:- Precisely controlled working distance between the sample and the tip using the AFM feedback loop-Electrochemical information corresponds to the local morphology (conductive tip works as electrode and AFM simultaneously).As the conductive tip we use commercially available boron-doped diamond (BDD) as well as Si AFM probes coated with the gold. The probes are insulated with a Si3N4 layer using plasma enhanced chemical vapour deposition. Before the formation of the active tip area the whole AFM probe has been coated with a chromium protection layer. Our self aligned approach for AFM-SECM tips formation comprises focused ion beam (FIB) machining and isotropic Inductively Coupled Plasma-Reactive Ion Etching (ICP-RIE). After the successful exposure of the conductive apex of the tip the protective Cr layer was removed by wet etching. Thereby we formed tips with nanoelectrodes of about 60 nm in diameter for a gold nanoelectrodes, and 200 nm in diameter for a BDD nanoelectrodes (the diameter of the as fabricated BDD AFM probe), both being chemically stable.By pre-shaping of the commercially available AFM tips we were able to form high aspect ratio AFM-SECM tips with diameters less than 60 nm. The length of the nanoelectrode can be freely adjusted between 0 and few µm in a well controlled manner.After the modification the AFM-SECM sensors were mounted into an AFM liquid cell, serving as the AFM probe and the working electrode. The electro-chemical characterization proved perfect insulating properties of the Si3N4 layer, as well as the perfect chemical stability of the BDD which is a new step for imaging in harsh environments.This reliable fabrication process with the reduced FIB usage makes the batch processing easier and is cost saving.
3:30 PM - VV2.4
Advances in Nanometer Scale Manufacturing Using Heated Atomic Force Microscope Probes.
Jonathan Felts 1 , Patrick Fletcher 1 , James Pikul 1 , Suhas Somnath 1 , Bikram Bhatia 1 , Nicholas Maniscalco 1 , Zhenting Dai 1 , William King 1 Show Abstract
1 Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States
We report advances in nanometer-scale manufacturing using heated atomic force microscope (AFM) cantilever tips. When the tip of a heated AFM cantilever is in contact with a solid surface, size of the heated contact area can be as small as a few nanometers. Within this ultra-small hotspot, it is possible to control thermally-activated chemical reactions, surface melting or decomposition, or thermal deposition of solid meltable materials. While there have been exciting small-scale demonstrations of this technology, there remains significant challenges to industrial scale implementation. These challenges include tip wear, controlling chemistry on and near the tip, thermal and mechanical control of the cantilever, and metrology of nanofabricated structures. This presentation reports several new innovations that seek to overcome the challenges to industrial scale implementation of tip-based nanofabrication. We have developed heated atomic force microscope cantilevers with heaters integrated with nanocrystalline diamond tips. These diamond tips demonstrate almost zero wear and negligible fouling under harsh conditions. Even when heated to 400 C and applying 200 nN of contact force to surfaces of diamond or quartz, the tips show almost no wear at high scan speeds and long scan distances. To address control of chemistry, thermoelectrohydrodynamic jet printing can be used to deposit picogram quantities of polymer onto the tip or a substrate with micrometer-scale spatial control. Finally, a closed loop control has been implemented directly into our AFM controller to provide 0.2 C variation control on the temperature of the cantilever. We report fabricating hundreds of nanowires of poly(3-dodecylthiophene) with lengths of 3.2 and 2.0 μm, having better than 50 nm of positional accuracy over a 30 μm scan area. These advances in tip-based nano-manufacturing provide a robust framework for scaling up tip-based nanofabricated to industrial scales.
3:45 PM - VV2.5
The Fiber Force Probe: Using Nanowires to Gently Image Soft Materials.
Babak Sanii 1 , Paul Ashby 1 Show Abstract
1 Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, California, United States
Performing AFM on soft materials such as live cells in solution is challenging due to sample deformation by the tip. The intrinsic thermal force-noise of the cantilever determines the minimum imaging force and resulting deformation. Reducing the cantilever's cross section reduces its noise significantly and we developed a simple optical detection technique that allows the use of nanowires as cantilevers. The resulting reduction in force-noise in water is orders of magnitude gentler than conventional AFM. This is a significant milestone towards non-invasive scanning probe imaging of biological processes on the surfaces of vesicles, suspended membranes, and live cells.
4:30 PM - VV2.6
AFM-Raman-SNOM and Tip Enhanced Raman Studies of Modern Nanostructures.
Pavel Dorozhkin 1 , Alexey Shchokin 1 , Evgenii Kuznetsov 1 , Sergey Timofeev 1 , Bykov Victor 1 Show Abstract
1 , NT-MDT Co., Zelenograd Moscow Russian Federation
We demonstrate results on various nanostructures (graphene, carbon nanotubes, semiconductor nanowires, quantum dots) studied by Confocal Raman/Fluorescence/Rayleigh Microscopy integrated with Atomic Force Microscopy (AFM) and SNOM. Graphene on gold is investigated by various AFM and spectroscopy techniques providing comprehensive information about the sample physical properties and composition. We study in details how the thickness (number of monolayers) in graphene affects its physical properties: surface potential (work function), local friction, elastic modulus, capacitance, conductivity, charge distribution, Raman and Rayleigh light scattering etc. Results for graphene flakes are qualitatively compared to those for carbon nanotubes of different diameters. We show how electrostatic charging of graphene flakes can be effectively measured and modified by AFM cantilever. Studies are performed both in ambient air conditions and in controlled atmosphere and humidity. AFM-Raman studies are also demonstrated for individual Si nanowires and carbon nanotubes. Light propagation phenomena in individual GaN nanowires is studied by AFM integrated with Scanning Near Field Optical Microscopy and Spectroscopy. We also present results of Tip Enhanced Raman Spectroscopy (TERS) or “nano-Raman” mapping realized using integrated AFM-Raman system. Measurements are realized in two different excitation configurations: Inverted (for transparent samples) and Upright (reflected light configuration, for opaque samples, with side illumination option). In both geometries we demonstrate near field Raman enhancement effect due to resonant interaction of light with localized surface plasmon at the apex of a metal AFM probe. Various samples are studied by TERS technique: thin metal oxide layers, fullerenes, strained silicon, carbon nanotubes, graphene. Actual plasmonic and near field nature of the Raman enhancement is proven by a number of ways: dependence of the enhancement on the excitation wavelength and polarization, enhancement versus tip-sample distance curves, observation of selective enhancement of Raman signal from thin surface layers of the sample etc. Finally, the ultimate performance of TERS is demonstrated by measuring Raman 2D maps with subwavelength lateral resolution (50 nm) – determined not by the wavelength of light, but by the localization area of the surface plasmon electromagnetic field.
4:45 PM - VV2.7
Parallel Scanning Near-field Photolithography: The Snomipede.
Ehtsham Haq 1 4 , Zhuming Liu 2 , Yuan Zhang 3 , Shahrul Alang Ahmad 1 , Lu-Shin Wong 5 , Steven Armes 1 , Jamie Hobbs 1 4 , Graham Leggett 1 , Jason Micklefield 5 , Clive Roberts 2 , John Weaver 3 Show Abstract
1 Department of Chemistry, University of Sheffield, Sheffield United Kingdom, 4 Department of Physics and Astronomy, University of Sheffield, Sheffield United Kingdom, 2 School of Pharmacy, University of Nottingham, Nottingham United Kingdom, 3 Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow United Kingdom, 5 School of Chemistry & Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester United Kingdom
The integration of top-down (lithographic) and bottom-up (synthetic) fabrication techniques remains one of the greatest unsolved challenges in molecular nanoscience: there are few techniques that provide control of chemical reactivity with nanometer spatial resolution, and few that also do so over macroscopic length scales. In scanning near field optical lithography (SNP), a scanning near-field optical microscope coupled to a UV laser is used to write patterns down to 9 nm . SNP has several advantages over other scanning probe techniques e.g. operation under ambient or fluid conditions (key for biological operations) and the ability to execute, directly, specific chemical transformations on a wide variety of surfaces. However, a drawback of any scanning probe technique is its serial nature (the probe writes only one feature at a time). Here we fuse the ‘Millipede’ concept, developed by Binnig and co-workers , with scanning near-field photolithography to yield a ‘Snomipede’ that is capable of executing parallel chemical transformations at high resolution over macroscopic areas of larger than a millimeter. Two designs are described. In the first, light beams (λ= 365 nm) generated by a liquid crystal spatial modulator are coupled to arrays of cantilever probes with hollow pyramidal tips. The individually steered diffraction-limited spots are controlled using optical tweezing software. Feedback may be detected from each probe in an array of up to sixteen probes, and each probe may be switched on or off independently, as required. The method is scalable and can work for more than hundred probes in parallel. In the second design, a digital mirror device is coupled to a Brewster-angle zone plate array. Again, writing may be selectively switched on or off, as required, at each probe. We demonstrate selective photodeprotection of nitrophenylpropyloxycarbonyl-protected aminosiloxane monolayers using nine probes operating in parallel across an area over 1 mm wide. A feature size of ca. 100 nm has been achieved. We demonstrate the subsequent growth of nanostructured polymer brushes by atom-transfer radical polymerization. The possibility of operating under liquid is demonstrated by writing parallel arrays of features with a resolution of 70 nm in photoresist with the entire cantilever array submerged under water. Such approaches offer a powerful means of integrating the top-down and bottom-up fabrication paradigms.Refrences:  S. Sun and G. J. Leggett, "Matching the resolution of Electron Beam Lithography using Scanning Near-field Photolithography", Nano Lett.4 (2004) 1381-1384. P. Vettiger, et al., ‘The ‘Millipede’—more than one thousand tips for futureAFM data storage, IBM J. Res. Dev. 44 (2000) 323–326.
5:00 PM - VV2.8
Nano-scale Strain Mapping using Near-field Microscopy.
Antonio Llopis 1 , Arkadii Krokhin 1 , Sergio Pereira 2 , Arup Neogi 1 Show Abstract
1 , Univ. of North Texas, Denton, Texas, United States, 2 CICECO, Univ. of Aveiro, Aveiro Portugal
Advances in nanophotonics are beginning to allow for the creation of nano-scale light emitting devices. Improving the quality of these next-generation emitters requires similarly advanced methods for characterization. These techniques need to be capable of imaging operational prototypes with nanometric resolution. For nano-scale emitters, the strain of the system can reveal a wealth of information about the quality of growth and defects. Unfortunately, current methods for mapping strain either lack the resolution needed (XRD), or are destructive in nature (TEM). We demonstrate here a new method for mapping strain capable of meeting the demands of next-generation device characterization. This technique makes use of near-field microscopy along with theoretical modelling to achieve non-destructive strain mapping with a resolution on the order of 10-100nm.We present results of experimental near-field photoluminescence measurements in an InGaN/GaN MQW system using a Jasco NFS-330 SNOM. Using a 4-gaussian fitting model, we extract the intensities of the phonon-replicas from the near-field data, and use them to produce a near-field map of the electron-phonon (e-p) coupling strength. Using theoretical calculations we extract the relation between the biaxial strain εxx and the e-p coupling strength. Applying this relation to the previously created near-field map yields a nano-scale map of the strain. We verify the efficacy of method by comparing the average of the strain in the near-field map with the strain measured using XRD.In conclusion, we have presented a new method for imaging strain using near-field microscopy and theo-retical calculations. Combining strain mapping resolution between 10-100nm with functional device imaging, this approach provides a powerful tool for the characterization of nanophotonic devices.
5:15 PM - VV2.9
Infrared Imaging Spectrometry in an Atomic Force Microscope.
Beomjin Kwon 1 , Matthew Schulmerich 2 , Laura Elgass 2 , Rong Kong 2 , Sarah Holton 2 , Rohit Bhargava 2 , William King 1 Show Abstract
1 Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States, 2 Bioengineering, University of Illinois, Urbana, Illinois, United States
We report quantitative infrared (IR) microscopy by coupling a monochromator and temperature-sensitive microcantilever-equipped atomic force microscope (AFM). The system utilizes a standard globar (heated wire) configured with a dispersive grating and other optical elements to provide narrowband (monochromatic) light over the spectral range 4.5 and 20 µm with a wavelength dependent spectral resolution in the range 27-127 cm-1. The IR beam was modulated at 150 Hz using an optical chopper. The mid-IR light was focused to a 2.62 mm2 spot at the sample plane with a wavelength dependent fluence of 1.93-7.55 μW/mm2. Transmitted light was detected by a bimaterial microcantilever that can resolve femtojoule changes in thermal energy. We report combined nanotopography and infrared imaging. Topography of the samples was measured using tapping mode AFM. At each spatial position, IR spectra were measured via cantilever bending induced by local IR absorption. To quantify the spectral resolution and to show the spectroscopy capabilities of our system, spectra were independently measured for one micrometer thick films of polymethyl methacrylate (PMMA), polycarbonate, or SU-8 USAF 1951 optical targets on barium fluoride substrates. Mapping of the sample surface was conducted by moving the tip and recording transmitted IR intensity at each position. The results compare very well with Fourier transform infrared (FT-IR) spectroscopic imaging measurements at a spectral resolution of 32 cm-1. The spatial resolution of the IR mapping image is either 30 μm or 60 μm as dictated by the size of the cantilever. Using these methods we also report photothermal IR images and AFM topography of stratum corneum from engineered skin (barium fluoride substrates) as well as MCF-10A cells cultured in MatrigelTM extracellular matrix (BD Biosciences) derived from three-dimensional culture (calcium fluoride substrates). The near field transmitted energy can potentially increase the spatial resolution of the system beyond the Rayleigh criterion that is currently realized by far field measurements. The recorded data is related to the geometrical sampling and probe tip configuration. Our latest experimental and theoretical results will be presented.
5:30 PM - VV2.10
Multiprobe AFM Bio-Imaging: The Next Evolution in SPM.
Rimma Dichter 1 , Galina Fish 1 , Sofia Kokotov 1 , Hesham Taha 1 , David Lewis 1 , Aaron Lewis 2 Show Abstract
1 , Nanonics Imaging Ltd., Jerusalem Israel, 2 Department of Applied Physics Selim and Rachel Benin School of Engineering and Computer Science, The Hebrew University of Jerusalem, Jerusalem Israel
Atomic force microscopy (AFM) with tuning fork feedback is the best method of AFM imaging known today. This presentation will describe the operation of this feedback mechanism in liquid. This allows for live cell AFM and NSOM operation in physiological media with high Q factors and without severe damping effects or any optical or mechanical constraints or interference. The extension of this frequency modulation feedback mechanism to tuning fork based liquid operation allows for scanned probe microscopy (SPM) cellular imaging fully integrated with any optical microscope including upright, 4 pi or standard Raman microprobes. It also will be shown that water immersion objectives can now be used with SPM and that these new directions allow for the first time live cell bioimaging with NSOM in spite of the stiff cantilevers that are generally associated with NSOM probes. The advances reported in this presentation, along with additional innovations in probe and scanner developments, allow for the dream of multiprobe NSOM/SPM to be implemented in physiological media. The results of these efforts portend important advances in the application of SPM in structural and functional bioimaging.
5:45 PM - VV2.11
Digital Pulsed Force Mode AFM and Confocal Raman Microscopy in Drug-eluting Coatings Research.
Greg Haugstad 1 , Klaus Wormuth 2 Show Abstract
1 Characterization Facility, College of Sci/Eng, University of Minnesota, Minneapolis, Minnesota, United States, 2 , Surmodics, Inc., Eden Prairie, Minnesota, United States
Controlled release of amorphous drug from a polymer matrix depends intimately upon the degree of mixing of drug and polymer, the susceptibility of the drug to crystallization, and the ability of the drug to dissolve and diffuse through polymer/solvent. Ideally, characterization methods would follow these processes on the molecular level in situ and in real time. We move closer to this ideal state of characterization through application of two imaging methods: (1) digital pulsed force mode atomic force microscopy, for high-resolution (~1-10 nm) surface sensitivity, and (2) confocal microscopic Raman scattering, for somewhat lower resolution (~250-500 nm) mapping but with 3D spatial sensitivity. We examine two model spin-coated films (~1 µm thick) containing the drug dexamethasone dispersed either in poly(butyl methacrylate) homopolymer or a blend of poly(butyl methacrylate) and poly(lauryl methacrylate). The latter case provides the presence of both glassy and rubbery polymers. We describe aqueous-immersion studies of surface and subsurface structural changes due to drug elution over time frames ranging from a few minutes to tens of hours. These time scales are important to the performance of drug eluting coatings during and immediately after surgery. Revealed relationships between coating structure and release kinetics are useful to the development of drug-eluting coatings formulations.AFM findings include (a) the rapid replacement of a dominant subpopulation of ~200-nm diameter bumps, present in dry, as-cast films, by ~200-nm diameter nanoscale surface depressions, due to rapid elution of dexamethasone from a majority of “pockets”; (b) the slower appearance of a small number of additional depressions in place of the original bumps, and the growth then collapse of a larger number of remaining original bumps over a period of many hours, related to a much slower elution of dexamethasone from a minority of “pockets”. We propose that an unbreached, thin PBMA surface barrier results in a slower, diffusional release of drug (process b), whereas molecular-scale perforations in this barrier allow the rapid release of dexamethasone from the majority of pockets (process a). Raman microscopy findings include the immersion-induced formation of dexamethasone microcrystallites in the vicinity of PLMA. The lack of surface crystallites in AFM images indicates that Raman is sensing objects below the surface, likely interfacing with PLMA domains. We conclude that complementary digital pulsed force mode AFM and confocal Raman microscopy provide insights into the mechanisms of drug elution from, and crystallization within, biomedical coatings.
VV3: Poster Session: Electronic Measurements and Nanolithography
Monday PM, November 29, 2010
Exhibition Hall D (Hynes)
9:00 PM - VV3.1
Quantifying the Inelastic and Elastic Scattering Lengths of Nanometer Thick Cu and Ag Films Using Ballistic Electron Emission Microscopy.
John Garramone 1 , Joseph Abel 1 , Ilona Sitnitsky 1 , Vincent LaBella 1 Show Abstract
1 College of Nanoscale Science and Engineering, University at Albany, Albany, New York, United States
Sidewall and grain boundary scattering in nanoscale Cu-metal interconnects dramatically increases the resistance, which is detrimental to the overall device performance. Interstingly nm thick films of copper have shown a greater increase in resistivity with decreasing thickness than other metals such as silver and aluminum. For these reason, quantifying the scattering length of electrons in nm-thick structures of metals such as Cu and Ag is both technologically and fundamentally significant. A highly accurate method for studying hot electron transport on the nanometer length scale is ballistic electron emission microscopy (BEEM). BEEM is a three terminal scanning tunneling microscopy (STM) based technique, where electrons tunnel from a STM tip into the grounded metal base of a Schottky diode . The BEEM current is a measurement of the electrons that traverse the metal film and are collected in the semiconductor. Results from BEEM measurements of the hot electron attenuation length of the metal films will be presented. To complement the measurements, a Fermi liquid based model is utilized to extract the inelastic and elastic contributions to the scattering. The metal films are deposited on H-terminated Si(001) under high vacuum and ultra-high vacuum (UHV). The BEEM measurements are taken at 77K under UHV. Recently we fabricated a contact to the metal layer on the silicon utilizing standard lithography prior to deposition of the metal in UHV . This allowed for BEEM measurements to be performed in situ. The process utilized to fabricate this contact will be presented along with the in situ BEEM results.References:  L. D. Bell and W. J. Kaiser, Phys. Rev. Lett. 61 2368 (1988)  J. J. Garramone, et al., J. Vac. Sci. Technol. A (in press) (2010) J. J. Garramone, J. R. Abel, I. L. Sitnitsky, L. Zhao, I. Appelbaum, V. P. LaBella, Appl. Phys. Lett. 96 062105 (2010)
9:00 PM - VV3.10
Electrical Properties of TiO2 Nanotube by Conducting-AFM.
Hyunjung Shin 1 , Myungjun Kim 1 , Changdeuck Bae 1 Show Abstract
1 School of Advanced Materials Engineering, Kookmin Univ., Seoul Korea (the Republic of)
Titinum dioxide(TiO2) has extensively investigated due to its utilization and potential to a number of applications such as sensor, photocataysis and photovoltatic devices. Particularly, one-dimensional nanostructures, such as nanowires, nanorods, and nanotubes, are known for unique electrical properties along their axis and thereby serve as critical building block for emerging potential applications. Therefore, understanding fundamental concept about how diemensionality and size affect their physical properties is critical for the nanoscale electronic applications. Conductive atomic force microscopy (C-AFM) is a variant of AFM, which provides extremely high resolution in investigating the local electrical properties and chance to modify contact state depending on which materials are coated on the C-AFM tips. This study demonstrated the transport behavior of anatase TiO2 nanotubes (TNTs) successfully fabricated using atomic layer deposition (ALD) followed by thermal annealing. Schottky (Pt/Ti/TNT/Pt) and/or Ohmic (Pt/Ti/TNT/Ti/Pt) contacts to individual anatase TiO2 nanotube were made using C-AFM tips at the nanometer length scale. The ideality factor, Schottky barrier heights and inherent resistivity of individual TiO2 nanotubes have been compared to the values from large-area contacts, enabling diode with arrays of TiO2 nanotubes in parallel and conventional thin-film devices, respectively. The junction properties of both Ohmic and Schottky contacts in accordance with the conventional band theory, but the nanoscale contacts to individual TiO2 nanotubes reveal a deviation from conventional electrical contact characteristics. The results provide perspectives on application for TNTs as improved charge collectors.
9:00 PM - VV3.11
Nanoscale Polarization Switching across 180° Domain Wall in Barium Titanate.
Vasudeva Aravind 1 , Katyayani Seal 2 , Stephen Jesse 2 , Venkatraman Gopalan 3 , Sergei Kalinin 2 Show Abstract
1 Physics, Clarion University, Clarion, Pennsylvania, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 , Pennsylvania State University, University Park, Pennsylvania, United States
Polarization switching across 180° ferroelectric domain wall in single crystal BaTiO3 was studied using switching spectroscopy piezoresponse force microscopy (SSPFM). Acquisition of hysteresis loops across closely spaced grid points allows polarization switching parameters to be mapped in real space. Hysteresis loops obtained as the scanning probe microscope tip sweeps across the domain wall in barium titanate is compared with theoretical calculations and recent observations in lithium niobate. In particular, critical bias required for the nucleation of 2D domain in barium titanate (3V) and LNO (4V) are close, despite 2 orders of magnitude difference in bulk coercive fields.
9:00 PM - VV3.12
Measurement of Piezoelectric Transverse and Longitudinal Displacement with Atomic Force Microscopy for PZT Thick Films.
Yuta Kashiwagi 1 2 , Takashi Iijima 2 , Toru Aiso 3 , Takashi Yamamoto 4 , Ken Nishida 4 , Hiroshi Funakubo 5 , Takashi Nakajima 1 , Soichiro Okamura 1 Show Abstract
1 , Tokyo University of Science, Tokyo Japan, 2 , National Institute of Advanced Industrial Science and Technology , Tsukuba Japan, 3 , Toyo Corporation, Tokyo Japan, 4 , National Defense Academy, Yokosuka Japan, 5 , Tokyo Institute of Technology, Yokohama Japan
To apply piezoelectric films to microelectromechanical systems (MEMS), it is important to clarify the electric-field-induced transverse and longitudinal displacement of the piezoelectric films. In the case of a micro-actuator application such as cantilever devise, it is well known that the transverse piezoelectric effect (d31) is dominant. Therefore, transverse piezoelectric constant should be clarified to design the piezo-MEMS devise. Although many measurement methods of the longitudinal displacement for piezoelectric films were reported, measurement of transverse displacement has not been well investigated. In this study, the transverse and longitudinal displacement of the piezoelectric film was evaluated, and relation between measured effective piezoelectric constants d31, eff and d33, eff was investigated. The transverse and longitudinal displacement measurement system using AFM was developed for the piezoelectric thick films. A 5-µm-thick Pb(Zr0.53, Ti0.47)O3 (PZT) film was prepared on Pt/Ti/SiO2/Si substrates. The film sample was shaped square pillar with Pt top electrode. The side length of square pillar shaped sample was defined as L. Prepared L was ranged 10 µm to 1000 µm. The relation between the piezoelectric displacement and L was investigated. To measure the transverse displacement, a conductive AFM cantilever contacts the edge of the top electrode and applies electric field to the film. The transverse displacement is determined from the torsion feedback signal absolutely. To measure the longitudinal displacement, the AFM cantilever contacts the center of the top electrode. The longitudinal displacement was estimated with Z height feedback signal. When L was less than 20 µm, the transverse displacement increased linearly. However, when L ranged from 20 µm to 300 µm, the transverse displacement became slightly increase. When L was more than 300 µm, transverse displacement increased linearly again. This result indicates that the piezoelectric transverse displacement did not increase linearly with increasing L from 10 µm to 1000 µm because of the substrate clamping effect. This is the same tendency with the finite element method (FEM) simulation1). On the other hand, the longitudinal displacement continued to increase with decreasing L to 10 µm. This result indicates that the substrate clamping also affect the longitudinal displacement behavior. When L is 10 µm, measured effective piezoelectric constants were d33, eff = 236 pm/V, and d31, eff = - 50 pm/V. While measured d33, eff is close to bulk d33 (223 pm/V), measured d31, eff is less than bulk d31 (- 94 pm/V). These results suggest that the substrate clamping effect of transverse displacement is larger than that of longitudinal displacement.1) T. Yamamoto, M. Yamamoto, K. Nishida, H. Funakubo, T. Iijima, T. Aiso and Y. Ichikawa: Jpn. J. Appl. Phys. 48 (2009) 09KA04.
9:00 PM - VV3.13
Scanning Electrochemical Microscope as an Etching Tool for a Direct ITO Patterning.
Federico Grisotto 1 , Romain Metaye 1 , Bruno Jousselme 1 , Serge Palacin 1 , Julienne Charlier 1 , Adina Morozan 1 Show Abstract
1 Chemistry of Surfaces and Interfaces, CEA, Gif sur Yvette France
Indium tin oxide (ITO) is a wide band gap n-type semiconductor, known for its good transparency and relatively high conductivity when deposited as a thin film on glass or flexible transparent substrates. Fine patterning of ITO films is a necessity for the development of new display technology that requires transparent and conductive electrodes, such as bioelectronic sensing, micro-nano structuration for optical devices, pixels for LED - OLED displays, organic solar cells… To optimize the performances of such devices, clean patterning technique i.e. straight sidewalls and respect of surface chemistry and physical properties is needed. The main drawbacks of the existing patterning techniques (i.e. lift-off and wet or dry etching) are the uncontrollable sidewall shape, the surface contamination with ITO residues, the damages to the substrate, especially for flexible ones. This leads to a global degradation of the electrical and optical properties. Moreover, most of these techniques require the use of strong acids (halogen acid, aqua regal) or toxic gases (for plasma treatment) and are usually multi steps and high cost processes. We report here a simple and one step patterning technique of ITO using the scanning electrochemical microscopy as a soft etching tool. This direct lithographic technique provides a fast and low cost patterning process. Local etching of the ITO film is performed in aqueous acid electrolytic solution, in a SECM environment. This technique leads to a clean etching with straight walls and no redeposition of the ablated part. The subjacent substrate (glass or polymer) is not damaged by this technique and the electrical and optical properties of the ITO film are preserved
9:00 PM - VV3.14
Control of Nanoparticle Deposition with Atomic Force Based Electrophoresis.
Talia Yeshua 1 , Mila Palchan 1 , Hesham Taha 2 , Aaron Lewis 1 Show Abstract
1 Department of Applied Physics Selim and Rachel Benin School of Engineering and Computer Science, The Hebrew University of Jerusalem, Jerusalem Israel, 2 , Nanonics Imaging Ltd., Jerusalem Israel
Lithography based on scanning probe microscopic techniques has considerable potential for the accurate and localized deposition of material on the nanometer scale. A subset of this advancing field of research is the controlled deposition of metallic features with high purity and spatial accuracy. This is of great interest for circuit edit applications in the semiconductor industry to plasmonics and nanophotonics and to basic research in surface enhanced Raman scattering and nanobiophysics. Within the context of metal deposition we will review the development of fountain pen nanochemistry and its most recent emulation Atomic Force Controlled Capillary Electrophoresis (ACCE). Using this latter development we will demonstrate achievement of unprecedented control of nanoparticle deposition using a three electrode geometry. Three electrodes are attached one on the outside of the metal coated glass probe, one on the inside of the hollow probe in the solution containing the gold nanoparticles in the capillary and a third electrode on the surface where the writing takes place. The three electrodes provide electrical pulses for accurate control of the deposition and retraction of the liquid from the surface which . overcomes the lack of control seen in both dip pen lithography and fountain pen nanochemistry when the tip is in contact with the surface. With this development we will demonstrate depositing of single gold nanoparticle with size of 1.3 nm onto surfaces such as semiconductors.
9:00 PM - VV3.15
Exploring Carbon Nanotubes as High Resolution Heat Probes for Scanning Thermal Microscopy.
Peter Tovee 1 , Manuel Pumarol 1 , Kevin Kjoller 2 , Oleg Kolosov 1 Show Abstract
1 Physics, Lancaster University, Lancaster United Kingdom, 2 , Anasys Instruments, Santa Barbara, California, United States
Carbon Nanotubes (CNT) have already brought significant potential to Scanning Probe Microscopy as ultimate resolution probes . CNT’s extreme heat conductance as well as their outstanding mechanical properties suggests further exploration of their application in Scanning Thermal Microscopy (SThM). Clearly, the thicker is the CNT, the better is its performance as a heat guide and its mechanical stability, with the expense of the resolution deterioration. In order to better optimize the design of the new high resolution probes, we have developed a suite of models for (1) mechanical stability of the CNT probe in contact with the studied sample, and (2) a thermal performance of used microfabricated highly sensitive thermal probe (TP)  with and without CNT at its apex. A close to reality model of the SThM probe was created using COMSOL and simulation results were subsequently compared with the experimental data.At first, a probe with and without CNT, in-contact and out-of-contact with Silicon, Silicon Nitride and PMMA samples and for different values of tip-surface contact area was modelled. The larger the tip, the more heat was transferred as should be expected. The temperature jump between TP in-contact and out-of-contact with the sample being significantly larger in vacuum than in air, suggesting that a vacuum SThM system would produce better experimental results. Simulation results for the temperature difference of TP probe without CNT in and out-of-contact with the sample were compared with experimental values and showed similar values of 0.2K and 0.22K, respectively. All COMSOL models showed slightly higher temperature jump values than in the experiments which should be attributed to some factors not taken into account in the model. Dynamic response of the TP probe with and without CNT’s has also been explored. Both simulation COMSOL and experimental data showing response time of 0.1 ms, with temperature fairly constant after 1 ms. Finally, we also discuss the first pilot results of handling of CNT’s and their attachment to the SThM probes. Finally, we also discuss the first pilot results of handling of CNT’s and their attachment to the SThM probes and application of that approach to nanoscale thermal analysis. REFERENCES: Wilson, Neil R; Macpherson, Julie V; Carbon nanotube tips for atomic force microscopy, Nature nanotechnology Vol 4, 2009 page 483-491.  Anasys Instruments, ThermaLever probes, AN2-300, http://www.anasysinstruments.com/nano-TAprobes.pdf,Kyoung Joon Kim, William P. King; Thermal conduction between a heated microcantilever and a surrounding air environment, Applied Thermal Engineering 2009 Vol 29 pages 1631-1641.
9:00 PM - VV3.2
Using Electric Force Microscopy to Study Surface Induced Fluctuations above Organic Materials - a Novel Measurement of Local Charge Mobility.
Nikolas Hoepker 1 , Showkat Yazdanian 1 , Roger Loring 1 , John Marohn 1 Show Abstract
1 , Cornell University, Ithaca, New York, United States
The development of organic electronics calls for new tools to study organic thin films. By measuring the frequency noise experienced by a cantilever near a surface, we are able to microscopically probe organic materials. In previous work, we used custom-fabricated ultrasensitive cantilevers to measure frequency noise due to dielectric fluctuations as a function of cantilever height and voltage over polymers of various compositions and thicknesses. In parallel, we have developed a zero-free parameter linear-response theory of thermally induced dielectric fluctuations that successfully describes our observations. Having understood dielectric fluctuations, we are now investigating fluctuations induced by carrier motion in organic transistors. The ultimate goal is to extract the local charge mobility from these measurements. Comparing our observations to a calculation based on free diffusion, we find that while theory overestimates the observed fluctuations, it predicts the correct spectral shape and distance dependence of the fluctuations.
9:00 PM - VV3.3
Correlation of Structures and Surface Potential at Vanadyl Phthalocyanine / HOPG Interface.
Weiguang Xie 1 , Jin An 1 , Kun Xue 1 , Xi Wan 1 , Jun Du 1 , Jianbin Xu 1 Show Abstract
1 Department of Electronic Engineering, Chinese University of Hong Kong, Hong Kong China
Thickness dependent vanadyl phthalocyanine (VOPc) morphology and surface potential due to the changing between lying-down and tilted configuration at the interface of VOPc/HOPG are studied using scanning tunneling microscopy and scanning Kelvin probe microscopy. Transition from bilayers numbers dependent surface potential increase to orientation dependent surface potential inhomogeneity is observed at the same film at different thickness. We find that the surface potential change at the initial lying down bilayers can be described by the abrupt junction model. At thicker area, maximum energy difference of about 100 meV between different oriented VOPc molecules is observed, indicating that the boundaries would act as significant barriers for holes transfer.
9:00 PM - VV3.4
Mapping Conservative and Dissipative Magnetic Response of the Ordered Arrays of Ferromagnetic Nanostructures by the Band Excitation Magnetic Force Microscopy.
Senli Guo 1 , Stephen Jesse 1 2 , Nozomi Shirato 3 , Hare Krishna 4 5 , Anup Gangopadhyay 4 5 , Ramki Kalyanaraman 3 6 7 , Sergei Kalinin 1 2 Show Abstract
1 CNMS, Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 2 Materials Science and technology Division, Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 3 Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, United States, 4 Physics, University of Washington in St. Louis, St. Louis, Missouri, United States, 5 Center for materials Innovation, University of Washington in St. Louis, São João Del Rei , Minas Gerais, Brazil, 6 Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee, United States, 7 Sustainable Energy and Education Research Center, University of Tennessee, Knoxville, Tennessee, United States
The magnetic dissipation and inter-and intra domain interactions in the ordered arrays of ferromagnetic structures have been explored by the band excitation magnetic force microscopy (BE-MFM). Nanoscale patterns are formed by pulsed laser interference melting of ultrathin metal films on SiO2 substrates as a result of the competition between thermocapillary flow and dewetting. In band excitation, the SPM is excited using the frequency band containing the resonance peak of the cantilever. The subsequent simple-harmonic oscillator peak allows the conservative and dissipative parts of magnetic tip-surface interactions to be deconvoluted. The magnetization directions, domain structures and dissipation of pure Co, Ni and Cu0.5Co0.5 mixture nanoparticles and pure Co and Ni nanowires have been characterized by the band excitation (BE) magnetic force microscopy. Complex magnetic domains relevant to the size and shape of nanostructures and the domain switching behavior have been explored. Part of this research has been conducted at ORNL’s Center for Nanophase Materials Sciences sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. DOE.
9:00 PM - VV3.5
Development of a Scanning Near-field Microwave Microscope for Localized Magnetic Resonance Measurements.
Christian Long 1 , Jonghee Lee 1 , Stephen Kitt 1 , Samuel Lofland 2 , Ichiro Takeuchi 1 Show Abstract
1 , University of Maryland, College Park, Maryland, United States, 2 , Rowan University, Glassboro, New Jersey, United States
Ferromagnetic resonance (FMR) spectroscopy is a fundamental tool in the investigation of magnetic materials. Traditional FMR measurements are performed by placing a sample into a resonant cavity or waveguide and measuring the absorption of microwaves by the entire sample. The results of these traditional FMR measurements give an average of the properties of the entire sample. In order to improve the spatial resolution of this technique, we place the sample outside of a resonant cavity and then use near field microwave microscopy to couple the resonator to one small part of the sample at a time. Using this technique, we can scan the surface of a thin film or bulk sample and map out the magnetic properties of the sample as a function of position. Using near-field microwave microscopy, one can also simultaneously map out the local variations in the permittivity of the sample. As an example system, we explore a single crystal Ga:YIG Disk. FMR absorption spectra are collected as the probe tip is scanned over the sample surface and the absorption peaks are mapped out as a function of the probe tip position. It is found that the absorption peaks correspond to magnetostatic spin wave modes. In order to identify the spin wave modes, numerical simulations are carried out using the RKMAG software.This work was supported by the NSF-MRSEC at the University of Maryland, DMR 0520471.
9:00 PM - VV3.6
Development of Scanning Differential Potential Microscopy for Evaluation and Modeling of Electrical Contacts on Nanoscale Materials.
Seungbum Hong 1 , Alexandra Joshi-Imre 2 , Hongsik Park 3 , Bryan Huey 4 Show Abstract
1 Materials Science Division, Argonne National Laboratory, Lemont, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois, United States, 3 Division of Engineering, Brown University, Providence, Rhode Island, United States, 4 Institute of Materials Science, University of Connecticut, Providence, Rhode Island, United States
In nanoscale systems, making four terminals on the low-dimensional semiconductors is very challenging and the activities of measurement can change the physical properties of the measured materials. To measure the intrinsic properties of nanoscale materials and the contact effects in nanoscale devices and to minimize the effect of measurement, we propose the scanning differential potential microscopy (SDPM), which enables measuring local electrical properties of nanoscale materials with minimized parasitic effects and perturbation by probing. The setup utilizes a conductive two-tip probe, which is fabricated by a focused ion beam etching on Au coated Si3N4 probe. In this presentation, we describe the design and process of SDPM tips and their applications to SDPM measurements.
9:00 PM - VV3.7
Local Switching Characteristics near Macroscopic Defects in Ferroelectric Capacitors.
Amit Kumar 1 , Flavio Griggio 2 , Susan McKinstry 2 , Stephen Jesse 1 , Sergei Kalinin 1 Show Abstract
1 CNMS, Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 2 Materials Science and Eng., Pennsylvania State University, University Park, Pennsylvania, United States
Hysteretic response is a universal feature of random systems, ranging from strongly correlated oxides to structural (glasses, polymers), magnetic (spin glasses) or polar (dipole glass) to polycrystalline materials. Polycrystalline ferroelectrics capacitors offer a convenient model system, in which the dipole reorientation does not change the underlying crystallographic lattice, and hence is potentially reversible. At the same time, the strong coupling between polarization and strain (reversible lattice deformation) allows the dynamics to be studied locally. The polarization dynamics in polycrystalline ferroelectric capacitors with macroscopic cracks was studied using band excitation switching spectroscopy piezoresponse force microscopy. Spatially-resolved mapping of the hysteresis loops and extracted switching parameters clearly reveals variation of nucleation bias, vertical offset and imprint fields near the crack which has its origin in modified strain state near the crack. Theoretical modeling has been employed to simulate the electro-mechanical coupling effect in the ferroelectric capacitor near a crack and thereby estimate the effect of declamping on the switching parameters near the crack. Using PFM based First order reversal curves (FORC), we demonstrate local preisach density mapping in these capacitors near the cracked region. Different approaches including multi-variate analysis and functional fitting have been used to analyse the local preisach desity maps and illustrate the deviation in phenomenological switching parameters near the crack. This research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at ORNL by the Division of Scientific User Facilities, U.S. DOE.
9:00 PM - VV3.8
Imaging Three-dimensional Polarization of Ferroelectric Domain Structures in PbTiO3 Nanotubes using Piezoresponse Force Microscopy.
Sunmi Moon 1 , Gir-eun Choi 1 , Yunseok Kim 2 , Changdeuck Bae 1 , Hyunjun Yoo 1 , Youngjin Yoon 1 , Jooho Moon 3 , Jang-Sik Lee 4 , Seungbum Hong 5 , Kwangsoo Ko 6 , Hyunjung Shin 1 Show Abstract
1 National Research Lab. for Nanotubular Structures of Oxides, Center for Materials and Processes of Self-Assembly, and School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 2 , Max Planck Institute of Microstructure Physics, Halle Germany, 3 Department of Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of), 4 Center for Materials and Processes of Self-Assembly, and School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 5 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 6 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Ferroelectric nanostructures, mostly one-dimensional nanaotubes(NTs) and tubular nanomaterials, have attracted much attention because they are possible technical applications of the high-efficient, miniaturized nano-sensors, actuators, and nonvolatile memory devices. We fabricated ferroelectric PbTiO3(PTO) NTs by reacting crystalline anatase TiO2 NTs with gas-phase of PbO powder at 400 degree C. TiO2 NTs served as starting materials were fabricated by template-directed atomic layer deposition (ALD) process onto porous alumina membranes. The fabricated PTO NTs are crystalline, as observed by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SEAD). Furthermore, cross section HRTEM images and energy dispersive spectroscopy (EDS) mapping images show the evenly reacted PTO NTs. We used the technique of piezoresponse force microscopy (PFM) to study the local ferroelectric behavior and the three-dimensional polarization distribution of complex ferroelectric domain structures in the PTO NTs. Domain structures of PTO NTs were visualized in 3-D obtained along all three components of the x-, y- and z-axes from the lateral and vertical PFM images at in-plane angles of 0 degree and 90 degree. The typical piezoresponse mapping has information of only the polarization components of Px and Pz. Thus, its LPFM images should be recorded twice with/without physical rotation by 90 degree in order to obtain Py polarization component on our PTO NTs. The information of Px, Py, and Pz enables us to reconstruct the 3-D domain configuration. Interestingly, we found a region where a grain in NT has a seemingly single domain in terms of out-of-plane polarization information, but in fact a polydomains divided by 90° domain wall as evidenced by x- and y- axes in-plane polarization information. In addition, we found a single domain consisted of multiple grains, which demonstrates an example of decoupling of the domain boundary with the grain boundary in polycrystalline PTO NTs.
9:00 PM - VV3.9
Comparison of Si-rich nitride and Silicon oxynitride in Si/Oxide/Nitride/Oxide/Si (SONOS) Memory Devices by Temperature-Variable Kelvin Probe Force Microscopy.
Wonsup Choi 1 , Hyunjun Yoo 1 , Changdeuck Bae 1 , Jooho Moon 2 , Jang-Sik Lee 1 , Hyunjung Shin 1 Show Abstract
1 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of), 2 Department of Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of)
Silicon/Oxide/Nitride/Oxide/Silicon (SONOS) nonvolatile semiconductor is a promising material for low voltage operation, scaling capability and high endurance. To improve SONOS device characteristics, data retention, trapped charge distribution and its decay behavior, it is important to evaluate physical and electrical properties of trapped charges in the nitride layer. The stored charge in the SONOS memory device lies in isolated sites within the silicon nitride dielectric. Therefore, a considerable attention has been paid on nitride films by different scientific communities. In this study, we have extracted the trap energy, retention time and decay behavior of the Si-rich nitride and compared them with those of silicon oxynitride. Trapping behavior of charge carriers (both holes and electrons) in ultrathin nitride/oxide (tunneling oxide)/silicon (NOS) structures was studied by variable – temperature Kelvin probe microscopy (KPFM). The contact potential difference induced by electrons or holes trapped in the nitride layer can be directly measured by KPFM under high-vacuum conditions (~10-7 torr). Additionally, the spatial distribution dynamics of trapped charges was observed in the samples of different growth conditions and dielectric–stack structure by measuring the relaxation behavior at the elevated temperatures of 150-450°C. The KPFM study indicates that the trap energy of both the hole and electron for silicon oxynitride are 1.20eV and 1.21eV, respectively. The trap energy (both for holes and electrons) for Si-rich nitride layer is much lower compare to silicon oxynitride. The trap energy for hole and electron in Si-rich nitride are 0.82eV and 0.77eV, respectively. We also determined the charges decay behavior of Si–rich nitride and Silicon oxynitride. We can observe that the diffusion process is dominant in the Si-rich nitride. But silicon oxynitride shows decay phenomenon more dominant than diffusion process. The data retention time for commercial nonvolatile memories is typically ten years at the temperature range of 0-85°C. We have estimated the retention time both hole and electron, at the Si-rich nitride and silicon oxynitride sample. In this work can be very useful for the characteristic of SONOS memory.