Symposium Organizers
Bryan D. Huey University of Connecticut
Oleg V. Kolosov Lancaster University
Seungbum Hong Argonne National Laboratory
Hyunjung Shin Kookmin University
VV1: Molecular Studies
Session Chairs
Monday PM, 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
1 AFM Unit, Bruker Corporation, Goleta, California, United States
Show AbstractThe 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
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
Show AbstractWe 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
1 Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractWe 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
1 Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus Denmark
Show AbstractDeveloping 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 [1].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
1 Physics, Portland State University, Portland, Oregon, United States, 2 Physics, University of Technology, Chemnitz Germany, 3 Physics, Humboldt University, Berlin Germany
Show AbstractTraditional 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
1 , AIST-NT Inc, Novato, California, United States
Show AbstractData 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
1 , IBM Research - Zurich, Rueschlikon Switzerland, 2 Institute of Experimental and Applied Physics, University of Regensburg, Regensburg Germany
Show AbstractIt 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
1 , IBM Research Division, T. J. Watson Reseach Center, Yorktown Heights, New York, United States
Show AbstractScanning 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
Session Chairs
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
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
Show AbstractNanoscale 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
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
Show AbstractElectrostatic 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[1] 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. [1] 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
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
Show AbstractCombined 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
1 Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States
Show AbstractWe 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
1 Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractPerforming 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
1 , NT-MDT Co., Zelenograd Moscow Russian Federation
Show Abstract 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
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
Show AbstractThe 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 [1]. 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 [2], 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: [1] S. Sun and G. J. Leggett, "Matching the resolution of Electron Beam Lithography using Scanning Near-field Photolithography", Nano Lett.4 (2004) 1381-1384.[2] 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
1 , Univ. of North Texas, Denton, Texas, United States, 2 CICECO, Univ. of Aveiro, Aveiro Portugal
Show AbstractAdvances 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
1 Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States, 2 Bioengineering, University of Illinois, Urbana, Illinois, United States
Show Abstract 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
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
Show AbstractAtomic 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
1 Characterization Facility, College of Sci/Eng, University of Minnesota, Minneapolis, Minnesota, United States, 2 , Surmodics, Inc., Eden Prairie, Minnesota, United States
Show AbstractControlled 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
Session Chairs
Tuesday AM, November 30, 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
1 College of Nanoscale Science and Engineering, University at Albany, Albany, New York, United States
Show AbstractSidewall 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 [1]. 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[3]. 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 [2]. 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: [1] L. D. Bell and W. J. Kaiser, Phys. Rev. Lett. 61 2368 (1988) [2] J. J. Garramone, et al., J. Vac. Sci. Technol. A (in press) (2010)[3] 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
1 School of Advanced Materials Engineering, Kookmin Univ., Seoul Korea (the Republic of)
Show AbstractTitinum 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
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
Show Abstract 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
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
Show AbstractTo 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
1 Chemistry of Surfaces and Interfaces, CEA, Gif sur Yvette France
Show AbstractIndium 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
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
Show AbstractLithography 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
1 Physics, Lancaster University, Lancaster United Kingdom, 2 , Anasys Instruments, Santa Barbara, California, United States
Show AbstractCarbon Nanotubes (CNT) have already brought significant potential to Scanning Probe Microscopy as ultimate resolution probes [1]. 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) [2] 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:[1] Wilson, Neil R; Macpherson, Julie V; Carbon nanotube tips for atomic force microscopy, Nature nanotechnology Vol 4, 2009 page 483-491. [2] 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
1 , Cornell University, Ithaca, New York, United States
Show AbstractThe 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
1 Department of Electronic Engineering, Chinese University of Hong Kong, Hong Kong China
Show AbstractThickness 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
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
Show AbstractThe 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
1 , University of Maryland, College Park, Maryland, United States, 2 , Rowan University, Glassboro, New Jersey, United States
Show AbstractFerromagnetic 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
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
Show AbstractIn 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
1 CNMS, Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 2 Materials Science and Eng., Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractHysteretic 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
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)
Show AbstractFerroelectric 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
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)
Show AbstractSilicon/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.
Symposium Organizers
Bryan D. Huey University of Connecticut
Oleg V. Kolosov Lancaster University
Seungbum Hong Argonne National Laboratory
Hyunjung Shin Kookmin University
VV4: Thermal Measurements, Tribilogy, and Metrology
Session Chairs
Tuesday AM, November 30, 2010
Fairfax A (Sheraton)
9:00 AM - VV4.1
Nonlinear Interaction Imaging and Spectroscopy in Scanning Probe Microscopy.
Stephen Jesse 1 , Sergei Kalinin 1
1 Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge , Tennessee, United States
Show AbstractAll information about material properties acquired through scanning probe microscopy is derived from the measurements of interactions between the tip and the sample. Nearly every form of scanning probe technique developed to date is based on measuring and recording only the linear aspects of this interaction and disregarding nonlinear components. Though much can be derived from looking at only the linear interactions, there is perhaps more important information hidden within the nonlinear ones such as local field gradients, indentation forces, hysteresis associated with anelastic and ferroic effects etc.. Of particular value are the short range forces that are generated when the tip is closest to the surface. It is in this highly non-linear regime that that parameters related to local chemical identity exist. We have developed an atomic force microscope control and acquisition scheme that can determine both the linear and non-linear components of tip-surface interaction and thereby extract both the usual metrics of tip motion, such as amplitude, resonance, and dissipation, as well as the force-distance curves for arbitrary tip-surface interactions. This method is based on performing non-linear operations on measured data and including this in least-squares fit to a non-linear model. We will demonstrate this approach for modeled data, and experimental data including force-distance curves, tapping mode, piezo-response force microscopy (contact mode), and magnetic force microscopy (non-contact mode). The methodology developed here can be used as a general protocol applicable to the measurement and analysis of wide variety of oscillating systems.Research at Oak Ridge National Laboratory's Center for Nanophase Materials Sciences was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
9:15 AM - VV4.2
Cantilever Resonance Enhanced Photoacoustic Spectroscopic Microscopy with Mid-infrared Quantum Cascade Lasers.
Feng Lu 1 , Mikhail Belkin 1
1 Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas, United States
Show AbstractMid-infrared (mid-IR) spectroscopy with sub-wavelength resolution is of high interest for chemical and biological research. Several techniques have been developed for sub-wavelength mid-IR imaging, including apertureless scanning near-field optical microscopy [1] and near-field photoacoustic/photothermal microscopy [2,3]. The later utilizes deflection of an atomic force microscope (AFM) cantilever to detect local thermal expansion induced by absorbed mid-IR light. Previously, high-power laser systems were used to induce temperature changes of 10-100K in the absorbing parts of samples and produce detectable AFM signal [2,3]. However, such heating is likely to damage samples, especially biological ones. In addition, high-power mid-IR lasers are bulky, complex, and expensive. Here we demonstrate that photoacoustic microscopy may be implemented using much lower laser powers by moving the repetition rate of the laser pulses in resonance with the AFM cantilever resonant frequency and using lock-in detection. In this approach the AFM cantilever integrates contributions from many laser pulses. We demonstrate our approach using quantum cascade lasers (QCLs). Mid-IR QCLs are electrically-pumped semiconductor lasers that operate at room temperature and can be widely-tunable. In our experiments, a QCL (Daylight Solutions, Inc.) was operated in pulsed mode with 100ns pulses. The laser repetition rate was tunable from 1kHz to 250kHz by the power supply. The laser was tunable in the range 1575-1700 cm-1. A sample was placed onto a BaF2 substrate and the light was focused through the bottom of the substrate to an approximately 160μm-diameter spot. The pulse energy at the sample position was approximately 10 nJ/pulse. We used an XE-70 model AFM from Park System, Inc., with separated XY and Z scan modules. The AFM cantilevers (SHOCONA) were gold-coated to avoid light absorption and had the fundamental bending frequency (in contact with a sample) in the range 180-210 kHz. The quality factor for the cantilever bending mode in free space was approximately 100. The A-B signal of the AFM is sent to a lock-in amplifier with QCL pulse frequency being used as a reference. We used 2μm-thick SU-8 resin sample for the proof-of-concept demonstration. A 30 times lock-in signal enhancement was observed as the QCL pulse frequency was adjusted to coincide with the resonant frequency of the cantilever. We note that higher signal enhancement is expected using higher quality factor cantilevers. To obtain the sample spectrum, the laser wavelength was tuned and the lock-in signal was recorded. We obtained a high-quality spectrum that was in excellent agreement with a spectrum obtained with an infrared spectrometer. The spatial resolution of our system was estimated to be better than 200nm. This work was supported by the Robert A. Welch Foundation grant number F-1705.[1]. A. J. Huber et al., Nature Nanotech. 4, 153 (2009).[2]. A. Dazzi et al., Opt. Lett. 30, 2388 (2005). [3]. K Kjoller et al., Nanotechnology 21, 185705 (2010).
9:30 AM - **VV4.3
Atomic Force Microscope Cantilever Based Nanoscale Heat Transfer Measurements.
Arvind Narayanaswamy 1 , Ning Gu 1 , Carlo Canetta 1
1 , Columbia University, New York, New York, United States
Show AbstractThe microcantilever has been a faithful workhorse of the atomic force microscope since its invention more than two decades ago. One of the more popular methods of measuring cantilever deflection is the ``optical lever" method. In order to improve the sensitivity of the optical detection, the cantilevers are usually coated with a thin layer of gold or aluminum, resulting in a bi-material cantilver. The difference in coefficient of thermal expansion between the two materials results in an annoying thermal drift when used for force measurement or topological imaging. However, it is this property of the bi-material cantilever that also makes it an extremely sensitive thermometer.In this work, we will show how the bi-material cantilever can be used to make quantitative heat transfer measurements using near-field radiative transfer between a microsphere and a substrate as an example. These measurements results in ``heat transfer-distance" curves instead of ``force-distance" curves. Measurements of radiative transfer between a sphere and a flat substrate show the presence of strong near-field effects resulting in enhancement of heat transfer over the predictions of the Planck blackbody radiation theory. We have been able to identify unambiguously the contributions of electromagnetic surface phonon polaritons to near-field radiative transfer.
10:00 AM - VV4.4
Scanning Thermal Microprobe for Thermal and Thermoelectric Characterization at Contact and Noncontact Mode.
Yanliang Zhang 1 , Eduardo Castillo 1 , Theodorian Borca-Tasciuc 1 , Rutvik Mehta 2 , Ganpati Ramanath 2
1 Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractWe present a scanning thermal microprobe technique with microscale spatial resolution for simultaneous measurement of thermal conductivity (κ) and Seebeck coefficient (α) at contact mode and for κ measurement at noncontact mode. In this technique, a joule-heated V-shaped microwire that serves as heater and thermometer locally heats a sample region of 2-3 μm radius through tip-sample thermal transport dominated by air conduction. The average temperature rise of the probe linearly increases with the probe power, and the slope gives the probe effective thermal resistance Reff. The tip-sample thermal contact resistance Rc and contact radius b were quantitatively determined from measurements on two reference samples for the noncontact, intermediate contact and contact modes. For the contact mode measurement, the κ is extracted by importing the Reff values measured in contact mode and the calibrated Rc and b for this mode into a heat transfer model, and α from the DC Seebeck voltage measured between the probe and unheated regions of the sample. For the noncontact-mode measurement, the microprobe is brought within ~100 nm from the sample surface, and ballistic air conduction is utilized as the tip-sample thermal transport pathway. The κ is extracted by importing the Reff values measured at noncontact mode and the calibrated Rc and b at this mode into the heat transfer model. The noncontact technique eliminates uncertainties due to solid contact and liquid meniscus conduction, and circumvents probe wearing and would be attractive for probing delicate samples that may be damaged or altered during contact-mode probing. Applications of the technique on Bi2Te3 and Bi2Se3 thin films reveal consistent κ values for the measurements at contact and noncontact mode, and α within 2% of the values obtained by independent measurements. The κ values measured on dense nanostructured bulk Bi2Te3 and Sb2Te3 at both contact and noncontact mode are within 5% of the results measured by an independent steady state method.
10:15 AM - VV4.5
Advancing Scanning Thermal Microscopy – Controlling Tip-surface Interaction via Non-contact and Vacuum Measurements.
Manuel Pumarol 1 , Peter Tovee 1 , Oleg Kolosov 1
1 Physics, Lancaster University, Lancaster United Kingdom
Show AbstractThe study of nanoscale thermal properties by Scanning Thermal Microscopy (SThM) is strongly influenced by the nature of the atomic size contact between the probe tip and sample. Precise control of the contact geometry and environmental conditions of this junction are essential for improved sensitivity, measurement precision, and spatial resolution in SThM. Traditionally, thermal properties are measured by operating the SThM in contact mode and in ambient atmospheric conditions. The presence of additional channels of heat transfer, most significantly the water bridge and air heat conductivity, impacts both sensitivity, and resolution. A direct solid-solid contact provides most informative thermal data1. Contact SThM operation in vacuum has been demonstrated2. Nevertheless, operation in contact mode can also lead to the contamination or damage of soft samples and the SThM tip due to strong tip-samples interactions. Also, friction forces are known to increase in vacuum. Moreover, the contact size is invariably determined by the applied force. The combination of vacuum and dynamic SThM operation mode would be a perfect solution to bring an increased sensitivity, precision and lateral resolution to SThM without extra damage to the sample.For addressing these issues we have developed a dedicated high vacuum (HV) multifunctional scanning force microscope. Our SThM system can be operated dynamically in contact (ultrasonic force microscopy), intermittent contact, and non-contact AFM modes. In order to study the nature of the direct solid-solid heat conduction in tip-sample heat transfer, the SThM is operated in the active constant power mode excited via a DC + AC voltage applied to a resistive heater integrated at the probe end of a silicon cantilever probe with a sharp tip. Electrical and thermal response of the heated tip-sample system is studied using state-of-the art electronics operating at a frequency range from several kHz to several tens of MHz’s.Preliminary measurements in HV of the temperature ‘jump’ when the tip of the SThM probe comes into contact with the sample, shows that only about 3% of the heat is transferred to the sample. Thermal contact resistance (Rc) calculated for gold and Kapton is 1.78x106 °C/W, and 2.50x106 °C/W, respectively. For intermittent contact operation at 20% reduced amplitude Rc is 25% higher than the value at contact, and at 50% reduced amplitude is 15% higher. This data shows the importance of the nature of the contact formed between tip and sample, its dynamics, and its influence in determining the thermal properties of the sample. Examples of thermal imaging of polymeric and metallic samples in dynamic SThM in a controlled environment, as well as future applications of this method are discussed.[1] Shi, L; Majumdar, A; Microscale Thermophys. Eng. 5, 251 (2001).[2] Hinz, M; Marti, O; Gotsmann, B; Lantz, M A; Dürig, U, Appl. Phys. Lett. 92, 043122 (2008).
10:30 AM - VV4.6
Transition Temperature Microscopy: A New Technique for Probing the Nanoscale Thermal Properties of Coatings and Multi-layer Films.
Khoren Sahagian 1 , Kevin Kjoller 1 , Lou Germinario 3 , William King 2 , Roshan Shetty 1
1 , Anasys Instruments, Santa Barbara, California, United States, 3 , LG Analytical, Kingsport, Tennessee, United States, 2 , University of Illinois, Urbana, Illinois, United States
Show AbstractTransition Temperature Microscopy (TTM) is a novel local thermal analysis technique that maps spatial variations in thermal properties on length scales from millimeters to nanometers. Traditional bulk thermal analysis provides a sample-averaged result and cannot generally supply sufficient information about complex structures or heterogeneities within films or coatings. There currently exists a nanoscale thermal analysis (nano-TA) technique where a nanoscale thermal probe heats a localized region on the sample surface in order to measure its thermal properties, includingthermal transition temperatures like crystalline melting points and glass transitions. TTM enables these nano-TA measurements to be carried out rapidly at a succession of points, thus creating automated high resolution spatial maps of the thermal properties of a sample. In this paper, we present data on how Transition Temperature Microscopy can be used to characterize chemical andstructural heterogeneities and thereby generate vital information in applications ranging from coating defects, to in-situ property measurement of individual layers in multi-layered films, to the detection of gradients and interfaces.
10:45 AM - VV4.7
Thermal Scanning Probe Lithography as a Tool for Spatially Controlled Highly Localized Nanoscale Chemical Surface Functionalization.
Joost Duvigneau 1 , H. Schoenherr 2 , G. Julius Vancso 1
1 , Twente University, Enschede Netherlands, 2 , Siegen University, Siegen Germany
Show AbstractWe report on the development of Thermal Scanning Probe Lithography (TSPL, figure 1) as a new lithographic tool for local thermochemistry on tert-butyl acrylate based polymer films to afford platforms for controlled high molecular density coupling and surface-immobilization of biologically relevant molecules, such as proteins. TSPL was developed as an approach for the development of (bio)sensors and platforms for cell surface interaction studies. The advantages of the use of polymer thin film platforms include simple and reproducible fabrication and quasi 3D structure for maximum loading of biomolecules. In addition, established solution chemistry can be applied for bioconjugation. The thermally labile tert-butyl ester groups in tert-butyl acrylate based polymer platforms can be cleaved of at temperatures above 150 °C in air to render the platforms carboxylic acid group functional for further bioconjugation. Our platforms were designed such that at these elevated temperatures the thermo mechanical properties are sufficient to avoid plastic deformation during TSPL. So far areas small as 35 nanometer have been successfully thermally activated with TSPL.
11:30 AM - **VV4.8
Wear? Where? There! Seeing Atomic-scale Processes in Friction and Wear by Combining AFM and Electron Microscopy.
Robert Carpick 1 , Tevis D.B. Jacobs 2
1 Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractA lack of scientific understanding of nanoscale friction and wear is a primary limitation for small-scale devices such as atomic force microscopy (AFM) probes and micro- or nano-electronic mechanical systems with contacting surfaces, and is also relevant for understanding friction and wear in larger-scale contacts. Ultrastrong carbon-based materials can have exceptional friction and wear characteristics, but nanoscale studies are limited. I will describe measurements aimed at uncovering fundamental insights into friction and wear for these materials at the nanoscale. I will first focus on studies that quantify the nanoscale volume loss in sliding wear using AFM and periodic ex-situ transmission electron microscopy (TEM) imaging. We find that novel carbon-based AFM tip materials, including ultrananocyrstalline diamond (UNCD) and diamondlike carbon, exhibit superior wear resistance compared to conventional materials (silicon and silicon nitride)[1-3]. I will then present results from wear tests performed inside of the TEM using modified in-situ indentation techniques. This permits real-time visualization of the contact geometry and shape evolution of a single asperity with sliding over a countersurface. This allows us to measure wear with a higher degree of precision than previously possible. Insights comparing the wear resistance of carbon-based and Si-based materials, particularly in the context of atom-by-atom wear processes, will be discussed[4]. 1.Prevention of nanoscale wear in atomic force microscopy through the use of monolithic ultrananocrystalline diamond probes. J. Liu, D.S. Grierson, J. Notbohm, S. Li, S.D. O’Connor, K.T. Turner, R.W. Carpick, P. Jaroenapibal, A.V. Sumant, J.A. Carlisle, N. Neelakantan & N. Moldovan, Small in press (2010).2.Ultra-low nanoscale wear through atom-by-atom attrition in silicon-containing diamond-like-carbon. H. Bhaskaran, B. Gotsmann, A. Sebastian, U. Drechsler, M. Lantz, M. Despont, P. Jaroenapibal, R.W. Carpick, Y. Chen & K. Sridharan, Nature Nanotechnology 5, 181-185 (2010).3.Wear resistant diamond nanoprobe tips with integrated silicon heater for tip-based nanomanufacturing. P.C. Fletcher, J.R. Felts, Z. Dai, T.D. Jacobs, H. Zeng, W. Lee, P.E. Sheehan, J.A. Carlisle, R.W. Carpick & W.P. King, ACS Nano 4, 3338-3344 (2010).4.On the application of transition state theory to atomic-scale wear. T.D. Jacobs, B. Gotsmann, M.A. Lantz & R.W. Carpick, Tribol. Lett. in press (2010).
12:00 PM - VV4.9
Elastic and Dissipative Shear Forces in AFM of Crystalline Organic Semiconductors.
Vivek Kalihari 2 , David Ellison 2 , Greg Haugstad 1 , C. Daniel Frisbie 2
2 Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 1 Characterization Facility, College of Sci/Eng, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractCrystalline structure is key to the performance of many organic optoelectronic materials. As with conventional inorganic semiconductors, crystallinity impacts electronic transport. But unlike inorganic semiconductors, intermolecular coupling is central to these soft systems, affecting both mechanical and electrical properties (e.g., hopping conduction). Relatedly, it has been known for more than a decade that friction force microscopy on soft materials is sensitive not only to differences in disorder (i.e., amorphous/crystalline) but also crystal anisotropy. This suggested that even elastic shear measurements should be useful to analyze crystalline organic systems. We have developed an understanding of elastic shear forces that are sensed transverse to the fast-scan axis in AFM on pentacene (a benchmark organic semiconductor) and related systems. We call this variant of AFM “transverse shear microscopy” (TSM).[1] That TSM has a different physical origin than frictional (dissipative) forces is implicated in scan velocity and temperature dependences (i.e., kinetics).[2] An elastic deformation model explains the anisotropy of the transverse shear force measured on a pentacene single crystal, establishing a connection to the in-plane elastic modulus tensor. Shear modulation force microscopy also contributes to this analysis, within a pinned contact.[3]In the thin-film case, a mosaic of crystallographic orientations of pentacene grains is revealed by TSM. Quantitative grain analysis is provided, including each grain’s crystallographic orientation and a tabulation of relative populations of low- and high-angle grain boundaries (important to electronic transport).[3] Moreover an unusual coincidence-II, rotational epitaxial relationship between first and second monolayers of pentacene is revealed by TSM.[4] This epitaxy is common to several insulating substrates,[5] as utilized at the gate of field effect transistors (FETs). Conventional friction force imaging in conjunction with acidic etching reveals the presence of line dislocations within a subset of second-monolayer grains of pentacene. During film growth, these dislocations result from stress build-up as single-crystal second-layer islands cross grain boundaries in the underlying first layer. The density of dislocation defects in the second layer as well as grain boundaries in the first and second layers should be critical to FET performance, given that overall conduction is dominated by electronic transport within those monolayers close to the gate electrode. [1] K. Puntambekar, J. Dong, G. Haugstad and C. D. Frisbie, Adv. Funct. Mater. 16, 879 (2006)[2] V. Kalihari, G. Haugstad and C. D. Frisbie, Phys. Rev. Lett. 104, 086102 (2010)[3] V. Kalihari, E. B. Tadmor, G. Haugstad and C. D. Frisbie, Adv. Mater. 20, 4033 (2008)[4] V. Kalihari, D. J. Ellison, G. Haugstad and C. D. Frisbie, Adv. Mater. 21, 1 (2009)[5] V. Kalihari, G. Haugstad and C. D. Frisbie, submitted
12:15 PM - VV4.10
Atomic Force Microscope Cantilevers for Quantitative Nanotribology.
Mark Reitsma 1 , Richard Gates 1 , Lawrence Friedman 1 , Robert Cook 1
1 Materials Science and Engineering Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, United States
Show AbstractThe ability of atomic force microscopy (AFM) to resolve small-scale surface forces, ranging from micronewtons to piconewtons, across a multitude of material types and environments, enables AFM to be utilized for many applications in which surface force phenomena can potentially dominate functional properties. Applications in which nanotribology (nanoscale friction and adhesion) issues are critical to functionality, control, and reliability include magnetic storage devices and their continued miniaturization, the manipulation of nanoparticles for biomedical and other applications, and the projected increase in utilization of class III and IV microelectromechanical systems, consisting of contacting and moving components. Despite the force realization potential of AFM, there remains a distinct lack of agreed methods for measuring surface forces quantitatively. In this work, we present prototype cantilevers that enable quantitative small-scale friction and adhesion force measurements to be performed using contact-mode AFM. The “Hammerhead” cantilevers provide an optical lever sensitivity calibration for normal (e.g., adhesion) and lateral (friction) forces, performed in situ along with force measurements. The cantilevers are compatible with commercial AFM instrumentation and can also be used to perform other AFM techniques such as contact imaging and dynamic mode operation.
12:30 PM - VV4.11
Circular Mode: A New AFM Mode for Investigating Surface Properties.
Olivier Noel 1 , Hussein Nasrallah 1 , Pierre-Emmanuel Mazeran 2
1 , University of Maine, Molecular Landscapes & Biophotonics Group, LPEC UMR 6087, Le Mans France, 2 , Mechanic of Surfaces Group, Laboratoire Roberval, UMR 6253 , Compiègne France
Show AbstractThe Atomic Force Microscopy (AFM) offers interesting opportunities for the measurement of surface properties at the nanometer scale. Nevertheless, in the classical imaging mode, data are acquired using back and forth displacements. This kind of displacement leads to stops of the tip/sample contact each time the sliding direction is inversed. During these stops, the contact evolves from a dynamic contact to a static contact. That leads to a change of the tip/sample contact characteristics during the collecting of the data, like for example, shear stress, adhesion force, and then total applied load. Hence, every experiment conducted by classical AFM modes could be affected by the duration of these stops that depends on the experimental conditions (frequency, scan size, friction force, contact stiffness...)Here, we present, for the first time, a new AFM mode called circular mode [1] that allows collecting data at different constant and continuous sliding velocities without any stops. Our methodology consists in implementing a circular displacement of the tip/sample contact at a constant sliding velocity. Another interesting point of this circular mode is that high sliding velocities (more than 1 mm/s) can be reached compared to the classical low sliding velocities (up to 10 μm/s) available in commercial AFM if no servo loop is required. Moreover, the circular mode can be coupled with classical operating modes, as for example, force spectrum. In this talk, we will present the principle and the advantages of this method, and as an example, we will report the evolution of friction and adhesive forces, at different constant sliding velocities, obtained and measured in air.[1] O.Noel et al.; submitted to Ultramicroscopy Aknowledgements :This work was entirely supported by ANR project number ANR-08-JCJC-0051-01
12:45 PM - VV4.12
High Speed Nanometrology.
Jamie Hobbs 1 , Andrew Humphris 2 , Jeremy Howard-Knight 1 , Bin Zhao 2 1 , Priyanka Kohli 2 , David Catto 2
1 Department of Physics and Astronomy, University of Sheffield, Sheffield United Kingdom, 2 , Infinitesima Ltd, Oxford United Kingdom
Show AbstractIf nanoscale manufacturing is to become a reality, a method for the rapid and accurate inspection of the resultant functional devices is required. In materials science there is a growing need for high throughput methods for measuring surface features and structure. Although atomic force microscopy (AFM) has the spatial resolution required, it is severely limited in scan speed, and the vertical (height) resolution is degraded when scan speed is increased. Here we present a new approach to AFM that makes a direct and feedback independent measurement of surface height by focussing a homodyne laser interferometer onto the back of the AFM tip. Combining this with a passive method for maintaining tip-sample contact [1], in which a pinning force applied between the tip and the sample allows the cantilever to respond at frequencies far greater than its first resonant mode [2], allows the measurement of surface topography to be de-coupled from the control over tip sample forces afforded by the feedback loop. As long as tip-sample contact is maintained a true height image, traceable to the wavelength of the interferometer laser, is produced, regardless of the action or inaction of the z-feedback loop or the high frequency response of the rest of the cantilever. This avoids the conventional bottleneck in scan speed coming from the response times of the feedback loop and the cantilever, and leaves the feedback free to be optimised for force control rather than topography measurement. High speed metrological images obtained at rates greater than 1 frame/s, lateral resolution better than 10 nm (tip limited) and vertical resolution of 0.1 nm, will be presented, focussing primarily on semiconductor devices. By coupling the technology with a large area resonant scan stage [3], true height images with scan areas of 40×40 μm2 can be collected at 1+ frame/s rates. Advantages of this novel approach to AFM beyond high speed imaging will also be discussed.1.ADL Humphris, MJ Miles, JK Hobbs, (2005) Appl. Phys. Lett. 86, 0341062.JP Howard-Knight and JK Hobbs (2008) Appl. Phys. Lett. 93, 1041013.B Zhao, J Howard-Knight, ADL Humphris, L Kailas, E Ratcliffe, S Foster, JK Hobbs, (2009) Rev. Sci. Inst. 80, 093707
VV5: Mechanics and Acoustics
Session Chairs
Tuesday PM, November 30, 2010
Fairfax A (Sheraton)
2:30 PM - **VV5.1
Mapping Mechanical Properties with Contact Resonance Force Microscopy.
Donna Hurley 1
1 , National Institute of Standards & Technology, Boulder, Colorado, United States
Show AbstractA critical need for realizing the full potential of nanotechnology applications in manufacturing is the ability to measure mechanical properties with nanoscale spatial resolution. Nanoscale images of local variations in properties yield valuable information about material homogeneity and provide size-appropriate data for predictive modeling of device performance. The atomic force microscope (AFM) is a natural tool for investigating mechanical properties due to its spatial resolution, scanning capability, and relative ease of use. However, most AFM methods that have been developed for this purpose can only produce qualitative indicators of relative properties. In contrast, a dynamic, contact-mode technique called contact resonance force microscopy (CR-FM) enables quantitative imaging—mapping—of nanoscale mechanical properties such as elastic modulus. Here, we describe the current state of CR-FM measurement techniques. We explain the basic principles of CR-FM and discuss different ways in which they have been implemented as practical imaging tools. We show how such mapping capabilities facilitate studies of nanoscale mechanical behavior in emerging applications, for instance evaluation of the fiber/matrix interphase region in composites. New extensions of the original approach that enable measurements and mapping of viscoelastic properties are also considered. Finally, we discuss the applicability of CR-FM to detection of buried (subsurface) defects and interfaces. The nanomechanical mapping capability enabled by CR-FM represents an essential tool for the development, production, and in-situ monitoring of today’s and tomorrow’s nanomaterials.
3:00 PM - VV5.2
Measuring Nanomechanical Properties of Polyolefin Materials: In Pursuit of Improved SPM-based Techniques.
Dalia Yablon 1 , Jean Grabowski 1 , Andy Tsou 1
1 , Exxonmobil Research and Engineering, Annandale, New Jersey, United States
Show AbstractUnderstanding nanomechanical properties of polymeric materials is critical to improve the understanding of structure-property relationships and ultimately the design of these materials that are ubiquitous in the consumer market. Polyolefin (primarily polyethylene[PE] and polypropylene[PP]) materials, blends, and composites possess complex structures of various length scales that are particularly amenable for characterization by SPM techniques. However, SPM techniques rely on complicated tip-sample interactions that must be effectively separated, understood, and modeled if we are to ultimately be able to identify and quantify specific materials and material properties at the nanoscale, especially when the materials span a wide range of properties as is typical in real-life consumer samples. We describe different approaches to this problem utilizing various AFM techniques including force curves, bimodal dual AC imaging and contact resonance imaging (dual AC resonance tracking or DART); these techniques are applied to PP/rubber and PP/PS blends yielding quantitative maps of various mechanical properties including conservative and dissipative tip-sample interactions that can then be converted into storage and loss moduli maps. In addition, these materials are imaged under tensile stress revealing information about the response of the blend interface and subsequent material deformation.
3:15 PM - VV5.3
Nanoscale Contact Resonance and Damping Characterization of Low-k Dielectric Materials.
Gheorghe Stan 1 , Sean King 2 , Robert Cook 1
1 Nanomechanical Properties Group, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Portland Technology Development, Intel Corporation, Hillsboro, Oregon, United States
Show AbstractNovel developments in material property engineering at the nanoscale are greatly accelerated by advanced measurement methods, and particularly by scanning probe microscopy techniques that provide local property measurements at this scale. For nanoscale mechanical property characterization, the applicability and capabilities of contact resonance atomic force microscopy (CR-AFM) have been extensively demonstrated on a large variety of nanostructured materials[1,2]. Based on observing the change in the resonance state of an AFM probe in contact with the material investigated, the CR-AFM signal is primarily converted into calibrated maps of elastic moduli. However, when compliant materials are probed, their viscoelastic properties can also contribute to the AFM tip-sample coupling and viscoelastic effects becomes incorporated into the resonant response of the cantilever. In this work, contact resonance and contact damping were probed by CR-AFM on various low dielectric constant (low-k) films and at the interface between copper interconnects and low-k dielectrics. Under a variable load, the subsurface response of these materials was investigated and in this way a depth dimension was added to the common CR-AFM surface characterization. Moreover, by considering the effect of the contact damping on the dynamics of the cantilever, theoretical correspondence between the measured resonance frequency shifts and dissipation on these materials was established.[1] G. Stan, S. W. King, and R. F. Cook, J. Mater. Res. 24, 2960 (2009).[2] G. Stan, S. Krylyuk, A. V. Davydov, and R. F. Cook, Nano Lett. 10, 2031 (2010).
4:00 PM - **VV5.4
In situ Atomic Force Microscopy Nanomechanical Testing and Nanofabrication.
Xiaodong Li 1
1 Department of Mechanical Engineering , University of South Carolina, Columbia, South Carolina, United States
Show AbstractAtomic force microscopy (AFM) has undergone rapid advancements since its invention over two decades ago. This talk presents state of the art in situ AFM nanomechanical testing and nanofabrication techniques spanning (1) probing the mechanical properties of individual one dimensional (1D) nanostructures, (2) mapping local, nanoscale strain fields, fracture and wear damage of nanostructured heterogeneous materials, and (3) fabricating three-dimensional (3D) nanostructures. The AFM cantilever probe has been used as a force/displacement sensor for in situ nanomechanical testing in conjunction with scanning electron microscopy (SEM). These methodologies are expected to lead to further advancements in AFM based nanomechanics and nanofabrication.
4:30 PM - VV5.5
Ultrasonic Force Microscopy Approaches for True Subsurface Imaging of Elastic Properties of Nanostructures.
Oleg Kolosov 1
1 Physics Department, Lancaster University, Lancaster United Kingdom
Show AbstractScanning probe microscopes (SPM’s) play indispensable role in modern nanoscale material science by enabling imaging of surfaces with close to atomic resolution. Unfortunately, ability of SPM’s to look below the surface is unavoidably limited. The attempts of genuine subsurface imaging of elastic features using various SPM approaches so far predominantly resulted in detection of strong inhomogeneities like voids.In particular, Ultrasonic Force Microscope (UFM) has been shown to detect strong subsurface inhomogeneities [1]. In UFM a high frequency (HF) ultrasonic vibration of few MHz is applied to the sample, forcing it to elastically “indent” itself against the dynamically frozen AFM tip positioned at the end of force sensitive cantilever. The contact between the tip and the sample then serves as a mechanical diode, detecting ultrasonic vibration. A variation of UFM is Heterodyne Force Microscopy (HFM) [2] and subsequent implementations [3] where two adjacent HF vibrations are detected by the nonlinear tip-surface contact.Our analysis of subsurface sensitivity of UFM and HFM shows that it originates in the interaction of the elastic field created by the SPM tip with the elastic inhomogeneity under the object’s surface (that can be linked with local composition and/ or local elastic strain), and affects mainly the amplitude component of both UFM or HFM response. Phase information available in HFM plays only a secondary role due to very large scale difference of the ultrasonic wavelength (~mm) to the discontinuity depth (~nm).In this paper, we report novel experimental results of true subsurface nanoscale resolution elastic imaging of a semiconductor quantum dot (QD) nanostructure (InAs quantum dots in GaAs matrix with approximately 20% difference in elastic moduli) under capping layer of 50 Å thickness. The surface topography had atomically flat growth terraces with no indication of underlying structures, whereas UFM images revealed clearly identifiable subsurface structures at variable magnifications with smallest observable subsurface feature of ~ 5nm.A unique feature of this approach was that it enabled nanoscale imaging with ~ 5 nm resoluton of elasticity of subsurface nanostructures in their natural non-disturbed environment. In particular, capped QD’s we directly observed in UFM were smaller than surface QD’s that confirms the observation obtained via destructive TEM investigation. Further expansion of this methodology, challenges and potential applications are also discussed.[1] Yamanaka, K., H. Ogiso and O. Kolosov, UFM for nanometer resolution subsurface imaging, APL 64(2): 178-80, (1994).[3] M T Cuberes, H E Assender, G A D Briggs and O V Kolosov, Heterodyne force microscopy, J. Phys. D: Appl. Phys. 33 (2000) 2347–2355[2] Diebold, A. C., Subsurface Imaging with Scanning Ultrasound Holography, Science 310(5745): 61-62, (2005). [4] A. Briggs and O. Kolosov, Acoustic Microscopy, 2nd edition, Oxford University Press, 2010.
4:45 PM - **VV5.6
The Crosstalk Eliminated (XE) Atomic Force Microscope and Advanced Nanotechnology Applications.
Sang-il Park 1
1 , Park Systems Corp., Suwon Korea (the Republic of)
Show AbstractAtomic Force Microscopy (AFM) has been widely used to measure and characterize the surface of a sample in the nanometer scale. In first generation AFMs, based on piezoelectric tube scanners, the scanner movements were coupled in such a way that motion in the XY plane directly influenced the scanner’s position and sensitivity in Z, and this influence varied at different scanner offsets and respective scan speeds. One of the latest advancements in AFM industry has been the elimination of this cross-talk in the XY scan. Here, the XY flexure scanner, driving a sample, is decoupled from the Z scanner to which a probe is attached. The new AFM platform has a highly orthogonal and ultra flat scan. These key attributes of the new AFM are central to the accurate and reproducible measurements for quantitative nanoscale metrology. Building upon the strength of the crosstalk eliminated (XE) platform, the new AFM adds the remarkable capability of non-contact AFM in ambient atmosphere by adopting a high speed Z scanner actuated by dedicated high force piezostacks. With a minimized drive mass, the new AFM has a higher Z-scan bandwidth and a faster Z-servo response than conventional AFMs. The new non-contact AFM enables an ideal methodology for non-destructive sample scanning with longer tip life. The design concept of the crosstalk eliminated (XE) AFM was utilized to support specific advanced nanotechnology applications: a) under-cut measurement by intentionally changing the angle of the Z scanner thereby enabling sidewall roughness characterization in the nanoscale for the first time, and b) polymer pen lithography for low-cost, high throughput nanoscale patterning. Dr. Sang-il Park is the Chairman and CEO of Park Systems Corporation, a leading manufacturer of Atomic Force Microscopes since 1997. Previously, Dr. Park founded Park Scientific Instruments, the first commercial manufacturer of Atomic Force Microscopes, where he served as the Chairman and CEO for 9 years from 1988 to 1997. Prior to founding Park Scientific, he worked with Prof. Cal Quate at Stanford University as a graduate student and research associate. Dr. Park has authored and co-authored numerous research papers, text books, and twenty four U.S. patents in the field of Atomic Force Microscopy. He received his Ph.D. in applied physics from Stanford University and his B.S. in physics from Seoul National University.
5:15 PM - VV5.7
Scanning Probe Microscopy with Diamond Tip in Tribo-nanolithoraphy.
Oleg Lysenko 1 , Vladimir Grushko 1 , Evgeni Mitskevich 1 , Athanasios Mamalis 2
1 , Institute for Superhard Materials, Kiev Ukraine, 2 , Project Center for Nanotechnology and Advanced Engineering, NRC “Demokritos”, Athens Greece
Show AbstractThe results in direct nano-patterning demonstrate potential of the SPM-based techniques that include surface scratching to create 3D nanostructures on the surface. Such techniques became known as tribo-nanolithoraphy [1] and are believed to be successfully implemented in the future nanofabrication industry. An important obstacle to this, however, is the effect of wear at the nanometer scale which is critical to the stability of tribo-nanolithoraphic processes. Such stability is achievable via in-depth theoretical and experimental studies of friction at nanoscale along with the development of pioneering equipment. Our work presents the results of experimental fabrication of nanostructures formed by nanoscratching with the use of the multifunctional scanning tunneling microscopy previously developed by the authors [2]. Authors were performed scratching of the silicon surface by using boron-doped diamond tip. Operation was undertaken in the same direction sequentially with the tip sliding a side of the groove by one of the tip’s facets and the consequent surface scanning. Although not being applicable to the non-conductive surfaces, the proposed technique has significant advantages. One advantage is related to the high stiffness of tunneling probe as compared to the stiffness of AFM cantilever. High stiffness and perpendicularity of the tip to the surface during indentation eliminates bending beam effects on the typical AFM and ensures machining effectiveness. Another advantage and distinction of the instrument is its ability to analyze each phase of nanocomposite surface separately. Purposely synthesized boron-doped single-crystal diamonds were used as a tip material. [2]. Boron dopants distribution in the tip’s working zone was studied by measuring voltage-current characteristics of tunneling between the tip and reference surface. This allows authors to choose tips with the localized conductive zone comparable in size with single atoms. Resolution of the STM surface scanning is 1 nm that considerably exceeds achievable by diamond tip-equipped AFM. [1] N.Kawasegi, et al., Nanotechnology 16, 1411 (2005).[2] O.Lysenko, et al., Diamond & Rel. Mat. 17, 1316-1319, (2008).
Symposium Organizers
Bryan D. Huey University of Connecticut
Oleg V. Kolosov Lancaster University
Seungbum Hong Argonne National Laboratory
Hyunjung Shin Kookmin University
VV8: Poster Session: Cells, Molecules, Mechanics, Particles and Probe/System/Technique Development
Session Chairs
Wednesday PM, December 01, 2010
Exhibition Hall D (Hynes)
VV6: Lithography, PFM and Microwave Methods
Session Chairs
Wednesday PM, December 01, 2010
Fairfax A (Sheraton)
9:00 AM - VV6.1
Understanding Atomic Force Microscope High-field Lithography: Experiments and Simulations.
Stephanie Vasko 1 2 , Adnan Kapetanovic 2 , Robert Hanlen 2 , Jessica Torrey 2 , Renyu Chen 3 , Wenjun Jiang 3 4 , Scott Dunham 3 , Marco Rolandi 2
1 Chemistry, The University of Washington, Seattle, Washington, United States, 2 Materials Science & Engineering, The University of Washington, Seattle, Washington, United States, 3 Electrical Engineering, The University of Washington, Seattle, Washington, United States, 4 Physics, The University of Washington, Seattle, Washington, United States
Show AbstractAtomic force microscope high-field (> 10^9 V/m) lithography can create carbonaceous features with nanoscale resolution as fast as 1 cm s-1 by reacting organic liquid precursors with a biased AFM tip. It is theorized that, in this unique nanoscale environment, the molecules fragment into carbon radicals that combine onto the sample surface. In this work, we investigate the chemical reactions occurring in the tip-sample gap when organometallic precursors are used. Using diphenylgermane and diphenylsilane, carbon-free silicon and germanium nanostructures (SIMS, x-ray PEEM, TEM) are fabricated. The lack of carbon content in these features indicates a well-defined chemical pathway that involves dissolution of the organic fragments from the precursors either as benzene or charged species. For this chemistry, we propose a model that involves electron capture and precursor fragmentation under the high electric field. To verify this model, we compare experimental data and simulations and investigate the effects of voltage, current, time, and precursor chemistry on nanostructure growth rate
9:15 AM - VV6.2
Direct Metal Nanofabrication by Electrochemical Atomic Force Microscopy Lithography using an Intermediate Self-Assembled Monolayer.
Haiwon Lee 1 2 , Gwangmin Kwon 2 , Jae Beom Yoo 1 , Haena Chu 1 , Jo-Won Lee 3
1 Chemistry, Hanyang University, Seoul Korea (the Republic of), 2 Nanotechnology, Hanyang University, Seoul Korea (the Republic of), 3 , The National Program for Tera-level Nanodevices, Seoul Korea (the Republic of)
Show AbstractThe direct metal nanofabrication method has recieved much attention due to be free from significant issues including deposition, etching and cost. We demonstrated the dominant direct metal nanofabrication method based on electrochemical atomic force microscopy (AFM) lithography with a spin-coated organometallic precursor resist. In order to entirely exclude unnecessary reactions in lithography and to facilitate the clear removal of residual materials after lithography, the intermediate layer, n-tridecylamine hydrochloride (TDA-HCl) self-assembled monolayer (SAM), bound with a Si substrate was successfully applied as a blocking layer and a sacrificial layer for a resist lift-off process. In particular, the SAM was clearly eliminated by DI water due to ionically binding with a substrate and it could make less surface contamination. And the only negative pulse input bias as one of factors determining the shape of metal structures formed well-connected line patterns with smaller copper clusters than one applied by a constant DC bias and other pulse biases with a positive bias. The fabricated nanowires were physically and electrically confirmed to be composed mainly of copper and well connected in large scale. The formed copper nanostructures were applied as a metal mask to etch Si and also various metal structures such as Ag, Cr, Cu and Pt were successfully fabricated by this process. This method will advance its practical use in promising applications such as catalysts, masks, and interconnectors for Si based-devices.
9:30 AM - **VV6.3
Mapping Ionic Currents on the Nanoscale: New Applications of Piezoresponse Force Microscopy and Spectroscopy.
Sergei Kalinin 1 , Nina Balke 1 , Amit Kumar 1 , Stephen Jesse 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractFunctionality of nanoionic devices such as electroresistive and memristive electronics, Li-ion batteries, and solid oxide fuel cells is directly based on the flows of mobile ions in solids. Despite the wealth of device-level and atomistic studies, little is known on the mesoscopic mechanisms of ion diffusion and electronic transport on the level of grains, interfaces, and extended defects. Correspondingly, the development of the capability for probing ionic transport on the nanometer scale is a key to deciphering complex interplay between structure, functionality, and performance in these systems. Here we demonstrate how Scanning Probe Microscopy can be utilized to measure ionic flows based on the strong strain-bias coupling in the system when local ionic concentrations are changed by electrical fields. The imaging capability, as well as time- and voltage spectroscopies analogous to traditional current based electrochemical characterization methods are developed. The reversible intercalation of Li and mapping electrochemical activity in LiCoO2 is demonstrated, illustrating higher Li diffusivity at non-basal planes and grain boundaries. In Si-anode device structure, the direct mapping of Li diffusion at extended defects and evolution of Li-activity with charge state is explored. The electrical field-dependence of Li mobility is studied to determine the critical bias required for the onset of electrochemical transformation, potentially allowing reaction and diffusion processes in the battery system to be separated at each location. The Scanning Probe Microscopy measurements are compared with classical characterization methods such as cyclic voltammetry and electrochemical impedance spectroscopy. Finally, potential for probing oxygen vacancy diffusion and kinetics of oxygen reduction reaction locally is discussed.This material is based upon work supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Part of worked is performed as a user proposal in the Center for Nanophase Materials Sciences at ORNL.
10:00 AM - VV6.4
Role of Grain Boundary in Ferroelectric Charge Compensation Studied by Angle-resolved Piezoresponse Force Microscopy.
Moonkyu Park 1 , Seungbum Hong 2 , Hyunwoo Choi 1 , Kwangsoo No 1
1 Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractWe present our study on the role of grain boundary in ferroelectric charge compensation and its impact on polarization switching in polycrystalline Pb(Zr0.25,Ti0.75)O3 (PZT) thin films, using angle-resolved piezoresponse force microscopy (AR-PFM). We constructed the ferroelectric domain configuration based on the in-/out-of-plane phase and amplitude images while rotating the sample around the film surface normal, from 0° to 180° with an interval of 10° between each domain image. We used Pt/Ir coated tips for AR-PFM while non-coated Si tips for topography acquisition. Subsequently, we constructed the ferroelectric domain configuration with the overlaid grain boundary to calculate the amount of polarization charges at the grain boundaries.We found net negative polarization charge (maximum 69 % of full polarization charge per one grain boundary) at the grain boundary, which is much lower than that found at charged domain boundaries inside a grain (maximum 200% of full polarization charge). We found a continuous change in the in-plane polarization variants both inside the grain and across the grain boundary, which is probably associated with the competing interactions of the electrostatic and strain energy. We believe that the less ferroelectric charges across the grain boundary is related to the presence of positively charged oxygen vacancies.
10:15 AM - VV6.5
SSWM: Scanning SWitching Microscopy for Nanoscale Domain Nucleation Mapping.
Gregory Santone 1 , Yasemin Kutes 1 , Vincent Palumbo 1 , Oleg Kolosov 2 , Bryan Huey 1
1 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 2 Physics, Lancaster University, Lancaster United Kingdom
Show AbstractA variety of techniques have lately been developed and implemented to characterize ferroelectric switching at the nanoscale based on piezo force microscopy. For example, hysteresis loops can be acquired in a pixel by pixel fashion, after which images can be reconstructed related to local switching energies. Movies of domain switching dynamics are also widely employed, monitoring local domain orientations during or following poling, revealing preferential domain nucleation sites, growth directions, and even energies. A new approach is presented here, Scanning SWitching Microscopy (SSwM), whereby the time to switch domains beneath a scanning probe microscopy tip is measured in a pixel-by-pixel fashion. In this manner, nucleation energies can be determined for an entire surface, as opposed to only at locations that nucleate first after which domain growth often consumes the surrounding media. By repeatedly switching single locations, switching fatigue can also be monitored in real time.
10:30 AM - VV6.6
Relaxation in Hysteresis Loops : A Tool to Differentiate Thermodynamic and Kinetics Controlled Processes.
Amit Kumar 1 , Stephen Jesse 1 , Donovan Leonard 1 , Albina Borisevich 1 , Sergei Kalinin 1
1 CNMS, Oak Ridge National Lab, Oak Ridge, Tennessee, United States
Show AbstractHysteretic 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. Most of the hysteresis studies including those involving ferroelectric switching and electrochemical strain mapping are currently done with little attention to relaxation kinetics. In this work, we demonstrate how the thermodynamics and kinetics controlled processes during switching and oxygen vacancy migration can be differentiated on the basis of relaxation of the signal during each hysteresis step. Spatially-resolved mapping of the hysteresis loops and relaxation studies at each hysteresis step has been performed in ferroelectric materials like bismuth ferrite and lead zirconate titanate (PZT) films as well as ionic electrolyte material yttrium stabilized zirconia (where electrochemical strain hysteresis is governed by oxygen vacancies). Exponential decay models have been applied to extract average relaxation coefficients and correlated maps of the relaxation parameters have been obtained. In PZT films, the relaxation shows a strong correlation with the domain structure while a lower effect is observed in bismuth ferrite films. In YSZ, the relaxation studies reveal hot spots with increased oxygen ion diffusivity. Thus, the relaxation studies associated with hysteresis can provide us a good insight into whether the process is controlled by thermodynamics or is dominated by kinetics. Portions of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.
11:15 AM - **VV6.7
Scanning Nonlinear Dielectric Microscopy.
Yasuo Cho 1
1 Research Institute of Electrical Communication, Tohoku University, Sendai Japan
Show AbstractIn recent years, we have developed and reported the use of scanning nonlinear dielectric microscopy (SNDM) for the measurement of the microscopic distribution of dielectric polarization. Since the technique can sense the dielectric polarity of the specimen, we can expect to resolve a single electric dipole moment of an atom. In this paper, SNDM with super-high resolution is reported. First, experimental results on the ferroelectric domain and visualization of charge stored in flash memories are shown following the theory and principle of SNDM. Next, a higher-order nonlinear dielectric imaging method (HO-SNDM), a three-dimensional (3D)-type of SNDM for measuring the 3D distribution of ferroelectric polarization and non contact SNDM (NC-SNDM) are proposed. Using NC-SNDM, we clearly resolve the electric dipole moment distribution of Si atoms on Si(111)7x7 surface by NC-SNDM under ultrahigh vacuum conditions. The dc-bias voltage dependence of the atomic dipole moment on Si(111)7x7 surface was measured and the directions and the magnitudes of dipole moments of Si atoms on the surface were revealed.Since the technique is applicable not only to semiconductors but also to both polar and non-polar dielectric insulator materials, SrTiO3 and TiO2 surfaces were also observed by NC-SNDM and we succeeded to resolve fullerene (C60) molecule and graphite (HOPG) atomic structure. Finally, as an application of SNDM, we will present an ultrahigh-density ferroelectric data storage system using SNDM as a pickup device and congruent lithium tantalate single crystal as a ferroelectric recording medium. A summarization made up of newest experimental data on our investigation for ferroelectric high density data storage will be reported.
11:45 AM - VV6.8
High Resolution Near-field Microwave Microscopy of Conducting and Dielectric Materials Using a Hybrid Scanning Tunneling/Near-field Microwave Microscope.
Jonghee Lee 1 , Christian Long 2 , Haitao Yang 3 , Xiao-Dong Xiang 3 , Ichiro Takeuchi 1
1 Materials Science and Engineering, University of Maryland, College Park, Maryland, United States, 2 Physics, University of Maryland, College Park, Maryland, United States, 3 , Intematix Corporation, Fremont, California, United States
Show AbstractWe have developed a hybrid scanning tunneling/near-field microwave microscope. The microscope combines an atomic resolution scanning tunneling microscope (STM) and a resonator-based near-field microwave microscope. The coaxial microwave resonator is integrated into the scanner head of the STM and electrically coupled to the sample through the STM tip. The resonator has a fundamental resonant frequency of 2.5 GHz and an unloaded quality factor of 600. While scanning over a sample surface, we can simultaneously monitor the DC tunneling current, the resonant frequency, and quality factor of the resonator. When the tip is within tunneling distance of a conducting sample, we find that it is possible to obtain atomic contrast in both the low frequency tunnel current and the microwave channels. The atomic contrast in the microwave channels is attributed to GHz frequency current through the tunnel junction. Atomically resolved images of HOPG and Au(111) surfaces are presented. For the insulating sample case, we use lock-in amplification to measure higher-order dielectric non-linearity. This allows us to surpass the spatial resolution of traditional linear near-field microwave microscopy and resolve nanometer-scale features. We resolve atomic steps and nanometer-scale surface defects of SrTiO3. This state-of-art hybrid microscope allows us to characterize GHz electrical impedance of a conducting sample at atomic length scale and dielectric property of an insulating sample at nanometer scale.
12:00 PM - VV6.9
Quantitative Imaging of Graphene Impedance with the Near-field Scanning Microwave Microscope.
Vladimir Talanov 1 , Eric Shaner 2 , Christopher Del Barga 3 , Lee Wickey 3 , Irakli Kalichava 3 , Edward Gonzales 2 , Aaron Gin 2 , Nikolai Kalugin 3
1 , Neocera, LLC, Beltsville, Maryland, United States, 2 Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 Materials Engineering Department, New Mexico Tech, Socorro, New Mexico, United States
Show AbstractGraphene has emerged as a promising material for high speed nano-electronics due to the relatively high carrier mobility that can be achieved. To further investigate electronic transport in graphene and reveal its potential for microwave applications [1], we employed a near-field scanning microwave microscope with the probe formed by an electrically open end of a 4 GHz half-lambda parallel-strip transmission line resonator [2]. Because of the balanced probe geometry, our microscope allows for truly localized quantitative characterization of various bulk and low-dimensional materials, with the response region defined by the one micron spacing between the two metallic strips at the probe tip. The single- and few-layer graphene flakes were fabricated by a mechanical cleavage method on 300-nm-thick silicon dioxide grown on low resistivity Si wafer. The flake thickness was determined using both AFM and Raman microscopies. We observe clear correlation between the near-field microwave and far-field optical images of graphene produced by the probe resonant frequency shift and thickness-defined color gradation, respectively. We show that the microwave response of graphene flakes is determined by the local sheet impedance, which is found to be predominantly active. Furthermore, we apply a quantitative electrodynamic model relating the probe resonant frequency shift to 2D conductivity of single- and few-layer graphene [3]. From fitting a model to the experimental data we evaluate graphene sheet resistance as a function of thickness. Near-field scanning microwave microscopy can simultaneously image location, geometry, thickness, and distribution of electrical properties of graphene without a need for device fabrication. The approach may be useful for design of graphene-based microwave transistors, quality control of large area graphene sheets, or investigation of chemical and electrical doping effects on graphene transport properties. We acknowledge support from the DOE Center for Integrated Nanotechnologies user support program (grant #U2008A061), from the NASA NM Space Grant Consortium program, and from the LANL-NMT MOU program supported by UCDRD. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04 94AL85000.[1] W. Kundhikanjana, K. Lai, H. Wang, H. Dai, M. A. Kelly, and Z.-X. Shen, Nano Lett. 9, 3762 (2009); Y.-M. Lin, C. Dimitrakopoulos, K. A. Jenkins, D. B. Farmer, H.-Y. Chiu, A. Grill, and Ph. Avouris, Science 327, 662 (2010). [2] V. V. Talanov, C. D. Barga, L. Wickey, I. Kalichava, E. Gonzales, E. A. Shaner, A. V. Gin, and N. G. Kalugin, to appear in ASC Nano (2010). [3] V. Ryzhii, A. Satou, M. S. Shur, J. Appl. Phys. 93, 10041 (2003); S. Kang, P. J. Burke, L. N. Pfeiffer, and K. W. West, Phys. Rev. B 71, 165312 (2005).
12:15 PM - VV6.10
Concerted Emission and Local Potentiometry of Light-Emitting Electrochemical Cells.
Deanna Rodovsky 1 2 , Obadiah Reid 3 , Liam Pingree 4 , David Ginger 3
1 Device Research, Konarka, Lowell, Massachusetts, United States, 2 Electronic Materials, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 3 Chemistry, University of Washington, Seattle, Washington, United States, 4 Phantom Works, Boeing, Seattle, Washington, United States
Show AbstractWe study the operation of polymer light-emitting electrochemical cells (LECs) by combining Scanning Kelvin Probe Microscopy (SKPM) with in situ imaging of the electroluminescence and photoluminescence on planar LECs. We will present the first ever data set allowing SKPM and electroluminescence to be correlated. By combining these techniques on the same device in the same apparatus we directly map the relationship between the spatial distribution of electroluminescence and the local potential profile across the device. We find that the electroluminescence is always associated with a region of potential drop in LECs made with poly[2-methoxy-5-(3’,7’-dimethyl-octyloxy)-p-phenylenevinylene (MDMO-PPV), poly(ethylene oxide) (PEO), and potassium trifluoromethanesulfonate (KTf). Nevertheless, depending on the electrode metal used, we also find significant potential drops at or near the electrode/organic interfaces. We study the effects of using different electrodes and show that both the electroluminescence and potential profiles are strongly dependent on the electrode work function for thin junctions operated at low potentials. These results indicate injection barriers can affect the operation of LECs even in the presence of doping.
12:30 PM - VV6.11
Photoinduced Temporal Change of Surface-Potential Undulation on Alq3 Thin Films Observed by Kelvin Probe Force Microscopy.
Kazunari Ozasa 1 , Hiromi Ito 1 , Mizuo Maeda 1 , Masahiko Hara 1
1 Advanced Science Institute, RIKEN, Saitama Japan
Show AbstractTris(8-hydroxyquinolinato) aluminum (III) (Alq3) is one of the major organic semiconductors for light emitting devices. When an Alq3 film is prepared by vacuum deposition in the dark, surface potential (SP) proportional to the film thickness is spontaneously formed. Photoexposure reduces the SP of Alq3. We have reported the dependence and mechanism of the photoinduced SP reduction [K.Ozasa et al., Appl.Phys.Lett., 93 (2008) 263304.]. Recently, we found that the spatial undulation of the SP grows first and then decreases with photoexposure. We traced the temporal change of SP undulation through cyclic measurement with Kelvin probe force microscopy (KFM) and photoexposure, as well as in situ localized photoexcitation with SNOM-KFM. Amorphous Alq3 films with various thicknesses up to 300 nm were formed on n-Si(001) by vacuum deposition at room temperature in the dark with a deposition rate of 0.15-0.2 nm/s. The topographic and SP- morphology were measured with a Kelvin probe force microscope with lift mode. Photoexcitation was carried out with a lamp light for probe positoining in KFM appratus, or with a blue laser through fiber probe of SNOM-KFM [K.Ozasa et al., J.Appl.Phys. 107 (2010) 103501]. For 100-nm thick Alq3 film, which showed average SP of 4.2 V, the undulation of SP was 13 mV (histogram width) with spatial size 200-400 nm, while the topographic morphology has spatial size 20-30 nm and height variation <2 nm. The difference in spatial sizes indicates that the origin of SP undulation is spatial nonuniformity in the dipole alignment of Alq3 molecules, not the film thickness fluctuations. The spatial size of SP undulation shows that the Alq3 dipole alignment has spatial correlation for 200-400 nm distances, although the mechanism of the correlation is unclear at the moment. The average SP depends linearly on Alq3 film thickness, while the amplitude of SP undulation shows sublinear dependence on the film thickness. When the film was photoexposed (approx. 10 mW/cm2), the SP undulation was first increased up to 29 mV at 60 s and then decreased below 7.5 mV after 350 s, while average SP value decreased monotonically. SP undulation pattern was changed gradually and continuously by the photoexposure. These behaviors strongly suggest that the photoexcited electron-hole pairs are drifted by electric field in the film, and captured by deep traps near the surface. By the localized photoexcitation through the fiber probe of SNOM-KFM, the drop of SP by light was limited within 3-4 um, and the SP undulation pattern out of the SP-drop region remained. This indicates a spatial limit in the movement of photoexcited carriers in Alq3 thin films.In summary, the SP undulation and its behavior during photoexposure observed with KFM or SNOM-KFM give useful information on the dipole moment distribution, carrier traps near the surface, and the dynamics of photoexcited carriers in Alq3 thin films.
12:45 PM - VV6.12
Nanoscale Electro-optical Measurements of Photovoltaic Materials using Scanning Probe Microscopy.
Behrang Hamadani 1 , Hua Xu 1 2 , Suyong Jung 1 2 , Paul Haney 1 , Nikolai Zhitenev 1
1 Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 2 Maryland NanoCenter, University of Maryland, College Park, Maryland, United States
Show AbstractThe efficiency of photovoltaic devices based on inorganic thin-films or organic polymer blends is often determined by the nanoscale structure and properties of internal and contact interfaces. Measurements of local photo-conductivity, along with other scanning probe based measurements, can link the structural properties to the performance providing the desired feedback for the device optimization. However, the nature of the tip-to-sample contact can be quite different from contact interfaces in devices strongly affecting the injection and collection of charge carriers and complicating the data analysis. Here, we present the characterization of photoconductive channels in a model bulk heterojunction organic solar cell based on a p-type polymer and n-type small molecule. We directly compare the properties of the tip-to-sample interface to the nanocontact interface. We explore the nanoscale photocurrent response on two complementary device architectures using conductive tips suitable for the appropriate charge (i.e., electrons vs. holes) collection. In addition to the measurements at the top surface, we examine the response from the bulk of the film using novel sectioning technique. Our results provide significant insight into the origin of nanoscale variations in photoresponse and nanoscale morphology of such materials.
VV7: Local Electronic and Conductivity Measurements
Session Chairs
Wednesday PM, December 01, 2010
Fairfax A (Sheraton)
2:30 PM - **VV7.1
The Next Generation in Electromagnetic Properties: From Conductance to Dielectric Function with Local Probes.
Matt Brukman 1 , Kendra Kathan 1 , Sanjini Nanayakara 1 , Dawn Bonnell 1
1 , The University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractRecent advances in variations of conductive tip scanning probe microscopy have demonstrated unexpectedly high spatial resolution, on the order of 1 nm. These results motivate questioning whether other electromagnetic properties can be probed at this level of spatial resolution. It would be particularly valuable to fields ranging from microelectronics to biophysics to be able to access complex dielectric function locally. To this end, we present several results that approach this goal. Specifically we demonstrate 3 measurements: 4th harmonic light detection in scattering near field optical microscopy, 2nd harmonic electrical detection in conductive tip atomic force microscopy, and torsionally stabilized nano impedance imaging in atomic force microscopy. These techniques are applied to multiple materials systems, including high k dielectric thin films, self assembled monolayer of porphyrin, and microcontact patterned peptide based nanostructures. We determine the real and imaginary contribution to the dielectric function of a single molecular layer, local variations in dielectric constant on oxide and organic films, the distinguish contributions to molecular polarization from electron transport in peptides. Comparison the theoretical calculations allows issues of sensitivity and spatial resolution to be discussed.
3:00 PM - VV7.2
Quantitative Analysis of Non-linear and Hysteretic I-V Curves in Conductive Atomic Force Microscopy.
Peter Maksymovych 1 , Minghu Pan 1 , Pu Yu 2 , Ramamoorthy Ramesh 2 , Arthur Baddorf 1 , Sergei Kalinin 1
1 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Materials Sciences and Engineering and Department of Physics, University of California Berkeley, Berkeley, California, United States
Show AbstractMany future applications can rely on unique phenomena that arise in wide-bandgap oxide and organic semiconductors when electron transport is coupled to oxygen vacancy chemistry, one or several coexisting order parameters and ionic conductivity. Conductive Atomic Force Microscopy (cAFM) is emerging as a potent probe of such properties, due to its ability to differentate between intrinsic and defect-mediated behaviors. Yet, interpretation of cAFM data is almost always complicated by uncertainties in the tip-surface junction, material parameters and a limited range of accessible electric field and temperature. We will discuss three novel approaches to local I-V spectroscopy using model examples of Pb(Zr0.2Ti0.8)O3 (PZT) and BiFeO3 (BFO) thin films. Both materials are excellent ferroelectrics and both exhibit rectifying I-V curves and a pronounced polarization-mediated electroresistance [1]. In the first approach we analyzed the bias- and temperature dependence of current normalized differential conductance as a descriptor of the transport mechanism. In contrast to traditional methods of shape analysis of I-V curves and temperature dependence, this method was found provide a conclusive differentiation between candidate transport mechanisms. The I-V curves were found to be determined by both interfacially (Fowler-Nordheim tunneling) and bulk-limited (Poole-Frenkel) transport mechanisms, depending on the bias-range and measurement temeperature [2]. The second approach involves spatially resolved analysis of the variations within individual I-V curves, uniquely enabled by sub-10 nm spatial resolution of cAFM in vacuum. When applied to PZT, this analysis revealed a crossover between two limiting transport mechanisms, manifested in the change of both the strength and spatial distribution of the disorder. Thus arises an intriguing opportunity to spatially resolve the electronic properties of the tip-surface junction as well as the bulk, and even bottom interface [2]. Finally, the third methodology relies on the use of a non-linear bias-waveform to acquire the I-V curve. When applied to I-V hystereses, found in resistive switching and memristors, the measurement can decouple the bias-dependence of the transport mechanism from the field-induced changes of the electronic state of the material. The three approaches are complementary and when combined, they have not only yielded unprecedented insight into electronic properties of PZT and BFO, but also revealed unique dynamics of the ferroelectric order parameter associated with polarization-controlled transport. Research conducted at Center for Nanophase Materials Sciences, sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. DOE.(1) Maksymovych et. al, Science 324 (1421) 2009.(2) Maksymovych et. al, “Identifying Mechanism of Local Electron Transport through Ferroelectric Oxide using Scanning Probe Microscopy”, Nano Lett. subm (2010).
3:15 PM - VV7.3
Measuring Ferroelectric and Electrical Transport Properties of Oxides at Elevated Temperature at the Nanoscale.
Maxim Nikiforov 1 , Patrick Fletcher 2 , Bikram Bhatia 2 , William King 2 , R. Ramesh 3 , Stephen Jesse 1 , Roger Proksch 4 , Sergei Kalinin 1
1 , Oak Ridge National Laboratory, Knoxville, Tennessee, United States, 2 , University of Illinois, Urbana-Champain, Illinois, United States, 3 , University of California, Berkeley, California, United States, 4 , Asylum Research, Santa Barbara, California, United States
Show AbstractTemperature-dependent piezoelectric properties and polarization dynamics in ferroelectric materials contain a wealth of information on intrinsic switching mechanisms, including activation energies for domain nucleation, wall motion and pinning, as well as polarization-mediated electrical properties. To date, multiple studies have explored the temperature-dependent polarization dynamics in ferroelectrics using piezo-response force microscopy experiments, in which the sample was heated uniformly. Here, we show recent results of piezo-electric and current transport property mapping using self-heating cantilevers which both locally heat and measure said properties.Combining localized heating and the capability for electrical measurements provides tremendous opportunity for studies of oxide compounds by eliminating macroscopic effects of heating on the sample. We focused our studies on several oxide systems such as monocrystalline BaTiO3 and doped-BiFeO3 films. On single-crystal BaTiO3 (100) we measured the change in piezo-electric properties as a function of tip heater power. These experiments help us understand the contrast formation mechanism in heat-assisted piezo-force microscopy. After performing a proof-of-concept experiment, studies on doped-BiFeO3 films were done. Those measurements studied electrical transport and piezo-electric properties as a function of temperature in ambient air with sub-100 nm resolution. The nano-scale localized heating combined with measurement of electrical properties allows exploration of the interplay between ferroelectric, transport, and thermal properties by varying probe temperature as well as probe electrical field at different frequencies.A portion of this research at Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. A portion of this research was sponsored by Asylum Research Co.
3:30 PM - VV7.4
Local Electrical Characteristics of Oligothiophene Crystal Islands Studied by Dual-Probe Atomic Force Microscopy.
Masaharu Hirose 1 , Eika Tsunemi 1 , Kei Kobayashi 2 , Hirofumi Yamada 1 , Kazumi Matsushige 1
1 Electronic Sci. & Eng., Kyoto Univ., Kyoto Japan, 2 , Office of Society-Academia Collaboration for Innovation, Kyoto Univ., Kyoto Japan
Show AbstractSince the electrical characteristics of organic field-effect transistors (OFETs) considerably depend on the film structure of the molecular gate channel, it is essentially important to control the molecular orientations in the film and to elucidate the intrinsic electrical properties of the molecule. However, the electrical measurements of the crystal grains are often hindered by the difficulty in an electrical connection between a specific grain and an electrode because the size of molecular crystals is typically on the order of microns. We have recently developed a dual-probe atomic force microscope (DP-AFM) having two AFM cantilevers, which allows us to perform electrical measurements without fabricating metal electrodes by bringing two conductive tips in contact with a desired crystal grain. Since the positions of the tips can be independently controlled in three axes on the order of ten nanometers, we can investigate the local electrical properties of the single crystal. In this study, the local transport characteristics on the oligothiophene (α-6T) crystalline islands using the DP-AFM system were successfully measured.We used a 100-nm-thick silicon oxide film, thermally grown on a silicon substrate, as a substrate for the deposition of α-6T. The substrate surface was made to have a periodic groove pattern with a period of 400-nm and a depth of 10 nm such that crystalline grains were preferentially grown along the groove. For the fabrication of the groove pattern the electron beam lithography and the following wet etching process were used. After the etching the substrate was rinsed with an organic solvent, dried in a flow of nitrogen gas and irradiated with UV and ozone for 30 minutes. Finally α-6T molecules were deposited at a substrate temperature of 120 °C in a vacuum chamber. The resultant crystal islands had a characteristic crystal habit which was strongly related to the groove pattern. We positioned two conductive AFM probes on the same α-6T single crystal island and measured local FET characteristics. The relative position of the probes was precisely determined from the overlap of the two simultaneously obtained topographic images with the probes in the dynamic mode. After the probe positioning, they were brought in contact with the single crystal island and used as drain/source electrodes. We measured the current between the probes while the gate voltage was applied to the backside of the silicon substrate. We found that the drain current versus voltage characteristics measured on α-6T single crystals showed p-type semiconductor characteristics. The hole mobilities calculated using the linear range were on the order of 10-4 cm2 V-1 s-1. We assumed for the calculation that the channel width was the same as the typical conductive AFM probe diameter (100 nm) and that the channel length was the distance between the probes (500 nm).
4:15 PM - VV7
Panel Discussion: “The panel will feature brief presentations about future directions for Scanning Probe Microscopy from industrial, academic, and government scientists. Once panelists have presented their insights, an open discussion with the audience will follow.” Participants: Robert Cook (NIST), Kevin Kjoller (Anasys Instruments), Sang-il Park (Park Systems), John Pethica (NPL-UK), Roger Proksch (Asylum Instruments), Chanmin Su (Veeco Instruments), Jane Zhu (DOE BES).
Show AbstractVV8: Poster Session: Cells, Molecules, Mechanics, Particles and Probe/System/Technique Development
Session Chairs
Thursday AM, December 02, 2010
Exhibition Hall D (Hynes)
9:00 PM - VV8.1
48 Hours of Control in Live Cell Experiments with AFM and ICM using New Environmental Chamber.
Sang-Joon Cho 1 , Goo-Eun Jung 1 , Bong-Hyung Lee 1 , Yong-Sung Cho 1
1 , Park Systems Corp., Suwon Korea (the Republic of)
Show AbstractAtomic Force Microscopy (AFM) has been developed to be a powerful measurement technique for nano scale science and technology, making enabling experiments which no one ever dreamed possible of a quarter century ago possible. It has been able to provide shown not only high-resolution imaging of biological structures below the optical limit and monitoring its dynamics and processes in physiological conditions have been possible but also certain limitations still exists in the field of bio-applications. In order to overcome these limitations, we introduce the XE-series AFM for advanced nanoscale metrology, which separates the z-scanner from the x-y scanner. The high performing separated z-scanner with state-of-the-art closed loop feedback system allows for true non-contact imaging in liquid and in air environments, and this significantly improves imaging of various samples including biological ones. The separated z-scanner also provides an excellent platform for developing other scanning probe microscope techniques such as Near-field Scanning Optical Microscopes (NSOM), Tip-enhanced Raman Spectroscopy, and Scanning Ion Conductance Microscopes (SICM). The glass micropipette which is used as the sensitive probe, instead of silicon based stylus, in SICM can glide over live cells while maintaining an absolute non-contact imaging mode, and by using electrochemical current feedback system it can to further enhance the biological sample images. However, the environmental control such as temperature, humidity, CO2 concentration, and pH, is essential for live cell experiments. Moreover, the contamination issue should be dealt seriously during scanning probe imaging. We have successfully imaged live cells and fixed cells with environmental control using both SICM and AFM modules at the same sample location. These advances in instrumentation will be utilized in various biomedical researches and become a new driving force for NanoBio Science and Drug Discovery.
9:00 PM - VV8.11
High Bandwidth Optical Detector for Scanning Probe Microscopy.
Richard Myers 1 , Richard Farrell 1 , Xuefeng Zhang 1 , James Munro 2
1 , Radiation Monitoring Devices, Inc., Watertown, Massachusetts, United States, 2 , Munro Design and Technology, Walworth, New York, United States
Show AbstractWith the maturation of ultra high-speed scanning systems, there is a desire to extend the detection bandwidth used in beam-deflection-based atomic force microscopy (AFM) sensors. Systems that can monitor higher vibration frequencies would promote the further development of multi-modal AMF, where the microcantilever’s higher-mode vibration frequencies are monitored. These higher modes can be used to resolve a diverse range of forces interacting between the probe and the surface. This extended spectral information can produce improved molecular recognition and allow studies of interaction chemistry that have, to date, been inaccessible. With the advancement of higher detection bandwidths, AFM imaging rates can be increased to improve studies of dynamic interactions and processes that require large scale surface interrogation.Current commercial AFM instruments are limited to bandwidths no greater than a few MHz due to the use of standard silicon position sensitive detectors (PSD). While some slight improvement could be made with development of amplification electronics, lower optical signal levels are expected due to the shorter sampling times or the reduced surface area of the high frequency cantilevers. This lower signal makes it nearly impossible for the current optical receiver technology to resolve the small cantilever movements at high frequencies. To overcome the limitation of the optical detection system, we have developed an optical quadrant array with greater than 100 MHz bandwidth and responsivity of over 300 A/W. When used in conjunction with low-cost, near infrared laser diodes and packaged with custom amplification electronics, a high sensitivity optical module can be produced with an ability to monitor light levels less than 100 nW while maintaining high position resolution. For this presentation, we will discuss the development of a custom high bandwidth PSD module. We will expand on the performance of the module along with information on how the instrument can promote the use of high-frequency AFM methods.
9:00 PM - VV8.12
Nanometer-Scale Temperature Measurements on AlGaN/GaN Devices Using Scanning Joule Expansion Microscopy.
Kyle Grosse 1 , William James 2 , Anusha Venkatachalam 2 , Samuel Graham 2 , William King 1
1 Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois, United States, 2 Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractThe development of electronic devices based on AlGaN/GaN heterojunctions has enabled both high speed and high power due to the large 2D electron gas, high field effect mobility, and large breakdown fields typical of these devices. While the performance of these devices has increase dramatically, their reliability remains a primary concern which is affected by the localized temperature rise found during operation. Presently, techniques such as micro-Raman Spectroscopy and transient thermoreflectance have provided methods by which both high spatial and temporal resolution of the thermal response of these devices can be obtained. However, additional advancements in thermal metrology are needed which can provide both temperature resolution less than 1K and submicron spatial resolution. In this work, we demonstrate the use of scanning joule expansion microscopy (SJEM) to image the thermal response of AlGaN/GaN devices. The devices were a transmission line model (TLM) device with a source to drain spacing of either 8 or 20 micrometers. The TLM devices were powered in pulse mode between 25 mW – 1.0 W RMS at 10kHz and a 20% duty cycle. The thermal response was measured by atomic force microscope scans of the device thermomechanical expansion, which corresponds to the device temperature, with 25 nm spatial resolution. The TLM reached temperatures well above 100 C and surface temperature gradients above 3 C / micrometer. The temperature measurements were compared to a full 3D finite element analysis of the TLM showing excellent agreement. The method demonstrates that SJEM can provide spatial resolutions less than 100 nm, temperature resolution less than 1 K, and temporal resolutions into the 10 kHz range. This type of temperature measurements offers unprecedented capabilities for exploring thermal phrnomena in AlGaN/GaN devices, especially the location and intensity of hotspots which cannot be indentified with conventional metrologies. The presentation will discuss further application of this technique to 6 finger high electron mobility structures and the implications of this method for analyzing GaN devices.
9:00 PM - VV8.13
The Thermoelectric Power of Confined Graphene Structures Grown on Cu Foil.
Sanghee Cho 1 , Ho-Ki Lyeo 1 , Dongmin Kang 1 , Chanyong Hwang 1 , Kwonjae Yoo 2 , Eun Kyoung Seo 3
1 , Korea Research Institute of Standards and Science, Daejeon Korea (the Republic of), 2 , Chungnam National University, Daejeon Korea (the Republic of), 3 Department of Chemistry, Yonsei University, Seoul Korea (the Republic of)
Show AbstractWe report experimental studies on the thermoelectric power (TEP) of multi-layer graphene grown on Cu foil by chemical vapor deposition. The TEP is locally measured using a newly developed scanning thermoelectric microscopy technique based on the ultra-high-vacuum atomic force microscopy. The technique enabled us to obtain two-dimensional maps of TEP simultaneously with topographic information at the nanometer scale. We measured the local thermoelectric voltage produced by a nano-sized contact between probe and sample which were maintained at different temperatures; we varied the sample temperature while maintaining the probe at ambient temperature. With the increasing sample temperature between 300 and 340K, the measured voltage was highly uniform on graphene terraces and linearly dependent on the applied temperature difference. The measured value on the terraces was nearly constant regardless of the terrace height and the sign was negative; we verified the microstructure of the graphene layers by observing atomic-resolution images. These results imply that the TEP of the graphene layers is constant and dominated by the thermoelectric contribution of electron. Occasionally, positive TEP region could be observed and we assign the region to a chunk of hydrocarbon because the atomic structure of graphene could not be observed. Confined structures surrounded by the p-type materials showed much larger TEP value by a factor of 3~4; the width of graphene terraces was 500~1000nm and the confined structure was ~100nm wide. The TEP polarity and atomic structure of the confined structure were still the same as graphene layers. The larger TEP in the structure could be due to two reasons: the already 2D electronic structure of graphene is confined in the all directions and thus the TEP is enhanced as expected for quantum structures. Secondly, we may attribute the larger TEP to the highly confined thermal spreading that leads to a larger temperature difference in the confined region. Nonetheless, our observation is extraordinary when one considers the possibly large thermal conductivity of graphene layers. The ability to measure two dimensional distribution of TEP at the nanoscale can be an important mean to reveal the unexplored properties of graphene.
9:00 PM - VV8.14
Controlled Growth and Positioning of Metal Nanoparticles via Scanning Probe Microscopy.
Elisangela Pinto 1 2 , Ana Gomes 2 , Carlos Pinheiro 2 , Luiz Ladeira 2 , Marcos Pimenta 2 , Bernardo R. Neves 2
1 , IFMG - Instituto Federal de Minas Gerais, Ouro Preto, Minas Gerais, Brazil, 2 Física, UFMG - Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
Show AbstractMetal nanoparticles (NPs) are an essential constituent of many processes that take place on the nanoscale: from inorganic catalysis to biosensor development. For some of these proposed processes to become a reality a few barriers must be overcome. Commonly, a missing feature is the ability to control both the growth and positioning of the metal NPs. Even though conventional chemical and electrochemical growth routes yield enormous amounts of NPs, placing these particles in their position of interest has been revealed to be a good challenge, and some approaches to achieve this goal have been reported. This work reports on a process of SPM-induced (and controlled) reduction of metal ions to metal nanoparticles on a polymer matrix. Gold, silver, nickel, and rhodium NPs have been successfully grown with the developed process using their respective salts/halides (HAuCl4, AgNO3, NiCl2, and RhCl3.3H2O) dissolved to a thin-film polymer matrix. Poly(vinyl pyrrolidone), PVP, and poly(vinyl alcohol), PVA, were both successfully employed throughout this work. The reduction is reached when a biased SPM metallic tip is brought into contact with the polymeric film surface (with metallic ions dissolved at the film). The control of relevant parameters (precursor concentration, bias voltage, pulse duration, and humidity) enables the accurate growth and positioning of a single NP or the growth of large dendrites formed by thousands of NPs. The metallic nature of these NPs is established via X-ray diffraction. Some initial applications of this process, such as enhanced of Raman spectrums (SERS – Surface-Enhanced Raman Spectroscopy) and decoration of carbon nanotubes with metal NPs, are also briefly demonstrated and discussed. The decoration of carbon nanotubes shows the possibility of controlled positioning of NPs. Many other applications of both the SPM-induced reduction process and the controlled growth and positioning of NPs may be derived from the present work.
9:00 PM - VV8.15
Simultaneous Manipulation and Imaging of Selected Nanoparticles with Atomic Force Microscope and Controlled Picking and Dropping Nanoparticles.
Suenne Kim 1 , Farbod Shafiei 1 , Daniel Ratchford 1 , Xiaoqin Li 1
1 Physics, University of Texas at Austin, Austin, Texas, United States
Show AbstractMethods for controlling the position of nanoparticles with the atomic force microscope (AFM) have been studied for over a decade [1]. Nanoparticle clusters assembled with AFM may find exciting applications in nanophotonics and nanoelectronics [2,3]. In conventional manipulation methods, the AFM is used either as a manipulation tool or an imaging tool, but not both at the same time. In this work, a new manipulation protocol has been developed based on an understanding of friction at the nanoscale [4]. First, the AFM feedback is turned off and a nanoparticle is pushed by the probe. This step reduces the static friction between the particle and the substrate. Second, by scanning the AFM in tapping mode, the selected nanoparticle is dribbled along the slow scan axis to a target position. The advantages of the new manipulation method includes: (i) visual guidance during the manipulation, eliminating the need to image the sample again and (ii) manipulation of multiple particles simultaneously. Additional nanomanipulation examples including picking up (dropping off) particles, assembly of hybrid structures and three-dimensional structures will be discussed. Such an approach could be a foundation for connecting nanoscale structures and photonics. [1] C. Baur et al. J. VAC. SCI. TECHNOL. B 15, 1577 (1998) [2] J. Fan et al. Science 328, 1135 (2010)[3] N. Engheta Science 317, 1698 (2007) [4] S. Kim et al. ACS Nano 3, 2989 (2009)
9:00 PM - VV8.2
Mechanics of Pulling an Individual Single-stranded DNA from a Carbon Nanotube Pore.
Valentin Lulevich 1 3 4 , Sangil Kim 2 , Costas Grigoropoulos 1 , Alex Noy 1 2 3
1 Mechanical Engineering, University of California, Berkeley, Berkeley, California, United States, 3 School of Natural Sciences, University of California, Merced, Merced, California, United States, 4 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 , Porifera, Inc. , Hayward, California, United States
Show AbstractHydrophobic and narrow carbon nanotubes (CNT) represent a unique example of a nearly frictionless nanoscale pore. These properties allow carbon nanotube membranes to support water flows more than three orders of magnitude higher than the values predicted from the continuum hydrodynamic models models [1]. Although researchers demonstrated that nanotube pores support efficient DNA transport, little is known about the interactions of a polymer chain with the CNT pore. We used Chemical Force Microscopy, an AFM-based interaction force measurement technique, to study the mechanics of pulling a single-stranded DNA oligomer chain from a nanotube pore. These measurements used an aligned array of CNTs encapsulated into a dense polymer matrix, that not only prevented CNT buckling, but also blocked DNA interaction with outer CNT walls. AFM experiments showed that DNA extraction from the CNT pore occurs at a nearly constant force, which is drastically different from the elastic behavior typically observed during polymer stretching in AFM experiments. We present a model that shows how the combination of the frictionless nanotube pore walls and an unfavorable DNA solvation energy produces the behavior observed in the experiment. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.References:1.Holt, J.K., et al., Fast mass transport through sub-2-nanometer carbon nanotubes. Science, 2006. 312(5776): p. 1034-1037.2.Gao, H.J. and Y. Kong, Simulation of DNA-nanotube interactions. Annual Review of Materials Research, 2004. 34: p. 123-150.
9:00 PM - VV8.3
Measuring Nanomechanical Properties with Atomic Force Microscopy by Nanoindentation and Mechanical Mapping.
Clara Almeida 1 , Carlos Achete 1 2
1 Materials Metrology Division, Inmetro, Duque de Caxias, Rio de Janeiro, Brazil, 2 Metalurgical and Materials Engeneering, UFRJ, Rio de Janeiro, RJ, Brazil
Show AbstractThe measurement of nanomechanical properties of materials with atomic force microscopes (AFM) has become possible due to the precise control of the microscope tip position and forces applied between the tip and the surface. Several AFM operational modes have been developed in the last few years giving new information regarding the materials properties such as: phase imaging in tapping mode, force modulation technique and nanoindentation using the AFM tip. However, it is known that nanoindentations with AFM are sensitive to the normal bending and lateral torsion of the microscope cantilever. Nevertheless, with a proper analysis of the microscope cantilever movement during nanoindentation a quantitative determination of the materials mechanical properties are achieved. In this work, the mechanical properties of polymers and crystals were measured with AFM nanoindentation. The cantilever vertical and lateral movements were independently acquired and analyzed during the nanoindentation. The tip torsion was attributed to a change from elastic to plastic deformation regimes during nanoindentation. An analysis of the lateral movement of the laser beam, associated with the cantilever torsion, may be used to determine the material yield stress. The mapping of mechanical properties was performed with force microscopy operated in a pulsed force mode. During elastic deformation regime, no significant contribution of the lateral torsion of the cantilever was observed, allowing the measurement of the elastic properties of the materials in nanoscale. Quantitative measurements were performed in amorphous and crystalline materials that deform by different mechanisms. In particular, results obtained in graphene with different number of layers will be discussed. Our results show that the AFM system is sensitive to the mechanical changes induced by a single carbon atomic layer. To conclude, we show that the mechanical properties of graphene are dependent on the number of graphene sheets.
9:00 PM - VV8.5
Nanoscale Mapping of Phase Separated Polyurethanes by Atomic Force Microscopy (AFM): From ‘Fingerprint Images’ to Quantitative Elastic Moduli.
Peter Schoen 1 , Kristof Bagdi 2 3 , Kinga Molnar 2 3 , Patrick Markus 4 , Bela Pukanszky 2 3 , G.Julius Vancso 1
1 Materials Science and Technology of Polymers , University of Twente, Enschede Netherlands, 2 Department of Physical Chemistry and Materials Science, Laboratory of Plastics and Rubber Technology, Budapest University of Technology and Economics, Budapest Hungary, 3 , Institute of Materials and Environmental Chemistry,Chemical Research Center, Hungarian Academy of Sciences, Budapest Hungary, 4 , Veeco Instruments B.V. , Breda Netherlands
Show AbstractThe micro phase separated nanoscale morphology of phase separated polyurethanes (PUs) was visualized by atomic force microscopy (AFM) height and phase imaging of smooth surfaces obtained by ultramicrotonomy. Novel dynamic imaging modes of AFM, including HarmoniX material mapping and Peak Force Tapping were used to asses the mechanical performance of phase separated polyurethanes quantitatively as a function of their molecular structure. PUs were obtained from 4,4'-methylenbis (phenyl isocyanate) (MDI), 1,4-butanediol (BD) and poly(tetrahydrofurane) polyether polyol (PTHF). The segmented polyether PUs with varying stoichiometric ratio of the isocyanate and hydroxyl groups were prepared to investigate the effect of molar mass, as well as the type and number of end-groups on their morphology. The PU samples studied show characteristic “fingerprint” AFM phase images. The values of surface elastic moduli were determined with nanoscale resolution and were in excellent agreement for both AFM modes. While tensile testing provides a bulk average value for the elastic modulus of the elastomers, the novel AFM based elastic moduli mappings introduced enable the study of surface stiffness with nanoscale resolution in a quantitative way.References(1) Tocha, E.; Janik, H.; Debowski, M.; Vancso, G. J. Morphology of polyurethanes revisited by complementary AFM and TEM, J. Macromol. Sci.-Phys., 1291-1304 (2002) (2) Vancso, G.J.; Schön, P.; Duvigneau, J., “What’s New in Atomic Force Microscopy of Polymers? An Update” Microscopy and Analysis. 23, 5-11 (2009)(3) Pukánszky, B. Jr; Bagdi, K.; Tovolgyi, Z.; Varga, J.; Botz, L.; Hudak, S.; Doczi, T., Pukánszky, B. Nanophase separation in segmented polyurethane elastomers: Effect of specific interactions on structure and properties. Eur. Polym. J. 44:(8), 2431-2438 (2008)(4) Bagdi, K.; Molnár, K.; Pukánszky, B.; Pukánszky, B. Thermal analysis of the structure of segmented polyurethane elastomers J Therm Anal Calorim. 98, 825 (2009)
9:00 PM - VV8.6
Nanoscale Friction of Au Nanoparticles Sliding on Graphite Substrates under Ambient Conditions.
Katelyn Grey 1 , Peter Staffier 2 , Christine Broadbridge 1 , Udo Schwarz 2 , Todd Schwendemann 1 2
1 Physics, Southern Connecticut State University, New Haven, Connecticut, United States, 2 Mechanical Engineering, Yale University, New Haven, Connecticut, United States
Show AbstractAmong the fundamental questions in tribology, understanding the frictional force dependence on contact area is of particular interest. To address this issue on the nanometer scale, previous studies have investigated the frictional resistance encountered during the controlled translation of various sizes of antimony nanoparticles while being pushed by the tip of an atomic force microscope [1]. Thereby, two distinct frictional states of particle sliding have been observed: While some particles show friction increasing linearly with contact area, which reinforces Amonton’s law at the nanoscale, other particles assume an almost frictionless or “superlubric” state [2]. It is the purpose of the current study to extend experimentation to other material systems by measuring the frictional resistance of gold nanoparticles using the same approach. The gold nanoparticles were deposited under ultrahigh vacuum conditions on an in-situ cleaved graphite surface. The sample was subsequently removed from vacuum to be imaged and manipulated under ambient conditions. The initial results of this study shown on this poster include exploring nanoparticle friction as a function of contact area and as well as characterizing nanoparticle structure by complementary electron microscopy imaging.
[1] A. Schirmeisen and U. D. Schwarz, ChemPhysChem 10, 2373 (2009).
[2] D. Dietzel et.al., Phys. Rev. Lett. 101, 125505 (2008).
9:00 PM - VV8.7
Effect of the Sliding Velocity on Adhesion and Friction Forces.
Hussein Nasrallah 1 , Pierre-Emmanuel Mazeran 2 , Olivier Noel 1
1 , University of Maine, Molecular Landscapes and biophotonics group, LPEC,CNRS-UMR 6087, , Le Mans France, 2 , Mechanic of Surfaces Group, Laboratoire Roberval, UMR 6253, , Compiegne France
Show AbstractCapillary forces play an important role in adhesion, friction and wear phenomena. The main point of this study is to contribute to a better understanding of the influence of the sliding speed on both adhesion and friction forces in a nanoscale contact.To achieve such a goal, we have implemented a new atomic force microscopy (AFM) mode (Circular AFM mode [1]) that allows the measuring of the adhesion and friction forces while the AFM tip is sliding at a constant sliding velocity (v > 1 mm / s). In a first step, the evolution of the adhesion force vs. the sliding velocity was investigated in air (relative humidity > 30%) on model surfaces. On hydrophilic surfaces, 3 regimes are observed: wet regime, intermediate regime and dry regime.We also report that the transition speed, which corresponds to the speed of the middle of the transition in the intermediate regime increases linearly with the static contact angle measured with water for the different studied substrates. This trend can be explained by an evolution of the volume of the capillary meniscus between the tip and the surface with the wetting surface properties. In a second step, friction measurements at different normal loads were conducted on model surfaces with different physical-chemical surface properties and different roughnesses. We observed that for low roughness surfaces (atomically flat surfaces as mica and HOPG, Ra < 0.1 nm), the friction coefficient increases linearly with the logarithm of the sliding speed. Whereas, for rough surfaces (Ra > 0.1 nm), the friction coefficient decreases linearly with the logarithm of the sliding speed. However, for any roughness ranges (Ra < 0.1 nm or Ra > 0.1 nm), the observed linear variation of the friction coefficient with the logarithm of the sliding speed has two regimes.Finally, we notice a linear relationship between the speed that corresponds to the beginning of the second regime of the friction coefficients and the static contact angle measured with water for the different studied substrates.Acknowledgements :This work was entirely supported by ANR project number ANR-08-JCJC-0051-01.[1] O.NOEL et al. submitted to Ultramicroscopy.
9:00 PM - VV8.9
Reconstruction of Overhang 3D Structure using 3D AFM for Nanometrology.
Sang-Joon Cho 1 , Jung-Min Lee 1 , Byung-Woon Ahn 1 , Joonhui Kim 1 , Sang-il Park 1
1 , Park Systems Corp., Suwon Korea (the Republic of)
Show AbstractA new atomic force microscope (AFM) for measuring three dimensional undercuts or overhang features was developed. Unlike other 3D AFMs using flared tips, this new system operates with conventional AFM sharp tips, and rotates z scanner ±40 degrees with respect to samples, which allows the cantilever to access not only vertical walls but also undercuts up to 40 degrees. The rotation is fully motorized and the z scanner is fixed by kinematic mounts with a pneumatic cylinder during imaging process. A vertical on-axis optical microscope remains fixed at each position of scanning and, therefore, vision of the sample is not lost during the whole scanning process. The images taken at each of three positions; +40 degrees, 0 degree and -40 degrees, are transformed and combined to produce one three dimensional data. The combination algorithm is very simple and easy to apply. We tested the new AFM system and found that it produces fast z servo response and high scan accuracy on a par with the fixed z scanner AFM.
Symposium Organizers
Bryan D. Huey University of Connecticut
Oleg V. Kolosov Lancaster University
Seungbum Hong Argonne National Laboratory
Hyunjung Shin Kookmin University
VV9: Atomic, Chemical, Molecular and Thermal Measurements
Session Chairs
Thursday AM, December 02, 2010
Fairfax A (Sheraton)
9:30 AM - **VV9.1
Multiparameter Imaging and Understanding the Role of the Tip.
John Pethica 1 , S. O'Brien 1 , A. Norris 1 , H. Ozer 1
1 Physics, Department of Geology, Dublin Ireland
Show AbstractThe structure and composition of the tip remains one of the most challenging aspects of scanning probe microscopy. It can be difficult to identify unknown structures and chemical species in atomic resolution images, because the tip atom species itself is unknown, yet can strongly affect the contrast observed. Here we report simultaneous AFM/STM of Rutile and Copper surfaces. The use of very small amplitudes (~0.02nm) allows us to acquire truly simultaneous tunneling topography, force gradient, barrier height and energy loss images.A variety of tip structures are stable, and tip changes drastically affect the contrast from the TiO2(110) surface. The majority of our STM images exhibit a corrugation contrast opposite to most of the existing literature. However, by comparing force gradient, tunnel barrier and current, it is possible to separate out the imaging mechanisms and identify atomic species. The energy dissipation signal also gives atomic resolution, but we find that this reflects only the corrugation in force across an image rather than sitespecific losses. The actual dissipation is likely to be taking place elsewhere than in the immediate tip zone. This agrees with some recent models which suggest that efficient coupling of loss processes to observable tip motion requires extended or softer structures. Some similarities to AFM observations of dissipation in fluids will be discussed.
10:00 AM - VV9.2
Three-Dimensional Atomic Force Microscopy: A New Approach to Chemical Imaging and Interaction Quantification on Surfaces.
Harry Monig 1 3 , Mehmet Baykara 1 , Todd Schwendemann 1 3 , Milica Todorovic 2 , Ruben Perez 2 , Eric Altman 3 , Udo Schwarz 1
1 Department of Mechanical Engineering and Center for Research on Interface Structures and Phenomena (CRISP), Yale University, New Haven, Connecticut, United States, 3 Department of Chemical Engineering and Center for Research on Interface Structures and Phenomena (CRISP), Yale University, New Haven, Connecticut, United States, 2 Departamento de Físcia Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid Spain
Show AbstractBy combining low temperature scanning tunneling and non-contact atomic force microscopy (STM/NC-AFM), it is possible to probe the tip-sample interaction through various information channels. In particular, recording the frequency shift in the three spatial dimensions allows through the post-acquisition application of a rigorous data analysis procedure to recover the three-dimensional force and energy fields of surfaces on an atomic scale [1,2]. This new method has been referred to as three-dimensional atomic force microscopy (3D-AFM) [3]. In this talk, 3D-AFM combined with simultaneously recorded tunneling current data has been employed to investigate the role of surface defects with regard to their catalytic properties, where we use the oxygen-reconstructed Cu(100) surface as a model system. The surface oxide layer of Cu(100) features domain boundaries and a distinct structure of the Cu and O sublattices that is ideally suited for such model investigations. We will show that the tip-specific 3D force fields provide valuable information about the nature of active sites while the combination of 3D-AFM with the complementary electronic information from the tunneling current allows to establishing the chemical identity of surface atoms. In order to clarify the different contrast modes, DFT total-energy calculations and non-equilibrium Green’s function (NEGF) methods for electronic transport have been applied to determine the tip-sample force interaction and the tunneling current for a large set of tip models [4,5]. These calculations provide insight into both the fundamentals of contrast formation seen in this experimental technique as well as the correlation between tip-sample forces and local chemical reactivity. [1] B. J. Albers et al., Nature Nanotechnology 4, 307 (2009)[2] B. J. Albers et al., Nanotechnology 20, 264002 (2009)[3] M. Z. Baykara et al., Advanced Materials, DOI: 10.1002/adma.200903909 (2010)[4] Y. Sugimoto et al., Nature 440, 46 (2007)[5] J. M. Blanco, F. Flores, and R. Perez, Prog. Surf. Sci 81, 403 (2006)
10:15 AM - VV9.3
Towards the Ultimate Resolution of Atomic Force Microscopy by Employing Functionalized Tips.
Nikolaj Moll 1 , Leo Gross 1 , Fabian Mohn 1 , Alessandro Curioni 1 , Gerhard Meyer 1
1 Zurich Research Laboratory, IBM Research, Rüschlikon Switzerland
Show AbstractBy functionalizing the tip of an atomic force microscope (AFM) with a molecule or an atom which significantly contributes to the tip-sample interaction, the resolution can be dramatically enhanced. The interaction and therefore the resolution crucially depend on the chemical nature of the tip termination. Molecules can be imaged with atomic resolution by employing tips functionalized with a single CO molecule. In this work, the interaction between the CO tip and the imaged molecule are studied with first principles calculations. The calculated frequency shifts compare very well with the experiment. The different energy contributions are analyzed, and the Pauli energy is computed. We demonstrate the source of the high resolution is Pauli repulsion, whereas van-der-Waals and electrostatic interactions only add a diffuse attractive background.
10:30 AM - VV9.4
Temperature Effects in Nanoscale Friction: Thermal Probes Reveal the Role of Capillary Bridges.
Christian Greiner 1 , Jonathan Felts 2 , Zhenting Dai 2 , William King 2 , Robert Carpick 1
1 Mechnical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2 Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractFriction force microscopy (FFM) is a powerful tool to investigate tribological contacts fundamentally at the level of single nanoscale asperities. So far, only a few FFM studies have been conducted as a function of temperature, most of which have been under cryogenic conditions; investigations above room temperature are scarce. As well, all published studies have involved heating the sample, not the tip. A heated tip is an alternate means to vary the contact temperature and is potentially more representative of the localized heating that can occur in a real tribological interface. Here, we used custom AFM probes with integrated solid-state heaters which allowed for the cantilever temperature to be controlled between room temperature and 650 °C, with the temperature variation achievable within milliseconds. We systematically investigated the nanotribological behavior of single asperity contacts between the silicon tip and both silicon and silicon oxide samples. We observed a strong effect whereby friction increased significantly with temperature and decreased with sliding velocity in humid conditions. This is in contrast to cryogenic measurements where the opposite trends were reported. Moreover, the dependence of friction on temperature and velocity is largely suppressed by operating in a dry nitrogen atmosphere. The behavior is reversible, indicating that the effects are not due to damage or modification of the tip or sample. The effects can be attributed to the thermally-activated nucleation of a capillary at the tip-sample contact. Results obtained by sequentially varying the velocity are well-fit using an Arrhenius analysis allowing the extraction of an energy barrier for the nucleation process. Moreover, real-time temperature variation during scanning provides time-resolved measurements of friction as the capillary forms and is also well fit using Arrhenius analysis. Not only do these results enable us to study the kinetics of capillary condensation at the tip-substrate interface but also demonstrate active control of friction forces and capillary nucleation. Environmental scanning electron microscopy was used to further confirm the existence of capillary bridges between the tip and substrate through direct imaging of the tip-sample contact.
10:45 AM - VV9.5
Thermal Mirages and Phonon Tunneling in Variable Temperature STM.
Igor Altfeder 1 , Andrey Voevodin 1 , Ajit Roy 1
1 , Air Force Research Laboratory, Wright-Patterson AFB , Ohio, United States
Show AbstractWe demonstrate that the temperature of the terminating CO-molecule at STM tip apex can be directly measured by inelastic electron tunneling spectroscopy, and this new technique of molecular thermometry can be implemented in VT-STM. A previously unknown mechanism of interfacial thermal transport, field-induced phonon tunneling, has been revealed by this technique. We found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is caused by interfacial electric field and thermally vibrating image charges, “thermal mirages”. By comparing experimental data and theory, we show that the thermal energy transmitted through atomically narrow vacuum gap due to thermal vibration of image charges exceeds, by ten orders of magnitude, the Planck’s thermal radiation energy.References: I. Altfeder, A. A. Voevodin, A. K. Roy, submitted to Physical Review Letters.
11:30 AM - **VV9.6
Image Force Microscopy of Molecular Resonance - A New Microscopy Principle.
H. Wickramasinghe 1 , Indrajith Rajapakse 1
1 Electrical Engineering and Computer Science, University of California Irvine, Irvine, California, United States
Show AbstractWe demonstrate a new technique in microscopy which extends the domain of AFM’s to optical spectroscopy at the nanometer scale. We show that molecular resonance of feature sizes down to the single molecular level can be detected and imaged purely by mechanical detection of the force gradient between the interaction of the optically driven molecular dipole and its mirror image in a Platinum coated scanning probe tip. This microscopy technique is extendable to obtain nanoscale spectroscopic information ranging from infrared to UV and RF.
12:00 PM - VV9.7
Adhesion at the Nano Scale: Chemical Force Imaging on Single Crystalline Zinc Oxide Surfaces.
Ozlem Ozcan 1 2 , Berkem Ozkaya 1 2 , Guido Grundmeier 1 2
1 Technical and Macromolecular Chemistry, University of Paderborn, Paderborn Germany, 2 Institute for Polymer Materials and Processes, University of Paderborn, Paderborn Germany
Show AbstractZinc oxide is a key material in adhesion and corrosion science since the adhesion and corrosion characteristics of widely used galvanized steel is dependent on the properties of the native zinc oxide layer covering its surface. Understanding zinc oxide chemistry and the interaction of organic functional groups with zinc oxide / hydroxide surfaces is of crucial importance in the development of new adhesives and coatings.
In this paper we are presenting the chemical force spectroscopy results on single crystalline ZnO surfaces. The surfaces were prepared under atmospheric conditions to ensure stability in real operation conditions and characterized using angle dependent X-Ray Photoelectron Spectroscopy (XPS) for their surface chemistry. For the chemical force spectroscopy experiments gold coated AFM cantilevers were functionalized by bi-functional thiol monolayers. As for the second functionality silanols, carboxylic acids and phosphonic acids were selected. The tip functionalization procedure was followed spectroscopically using polarization modulated infra red reflection adsorption spectroscopy (PM-IRRAS) on gold substrates prepared by thermal evaporation. Since the collected force data is strongly dependent on the tip size, tip diameter was determined by scanning electron microscopy (SEM) measurements.
Force – distance curves were measured with the functionalized cantilevers at a pH-range of 4 to 10, where ZnO is stable. The attractive and repulsive interaction upon approach and the strength of the adhesive forces during retraction were analyzed by a self-written program. The pH regions where the tip functionalities are deprotonated and the break-down of surface hydroxyl stabilization were reflected in force histograms and thus could be visualized.
The ex-situ analysis of adsorption was performed using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and X-Ray photoelectron spectroscopy (XPS) on respective organic monolayers prepared at different pH values. A great correlation was obtained with the chemical force spectroscopy results. The effects of ionic, van der Waals and hydrogen bonding interactions between the surface and the tip and the influence of the electric double layer on the adsorption behavior will be discussed in detail in light of the chemical force spectroscopy and ex-situ DRIFT results.
12:15 PM - VV9.8
AFM and KPFM Study of Effect of Cholesterol and Cortisol on Structure of Lipid Monolayers.
Erin Faught 1 , Elizabeth Drolle 1 , Brad Moores 1 , Matt Vijayan 1 , Lukas Eng 2 , Zoya Leonenko 1
1 , University of Waterloo, Waterloo, Ontario, Canada, 2 , Technical University Dresden, Dresden Germany
Show AbstractThe plasma membrane is a complex structure, composed primarily of phospholipids and other macromolecules, such as proteins, sterols and steroids, which define its complex functions. Phospholipid monolayers are widely used as convenient models to study plasma membrane. We investigated model lipid monolayers composed of dipalmitoylphosphatidyl-choline (DPPC) in order to elucidate effect of cholesterol and cortisol on the structure and properties of these model systems. Supported DPPC monolayers were prepared with Langmuir-Blodgett monolayer technique and imaged by Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy (KPFM). Frequency modulation KPFM technique (FM-KPFM) (1) based on electrostatic force gradient was used to measure local surface potential distribution in monolayers. This technique is performed by applying modulation frequency in addition to the resonance frequency of the cantilever and has been shown previously to have superior resolution for measuring surface potential in biomolecular films (2). We found that cholesterol and cortisol produced structural changes (nanoscale domains) both in topography and surface potential maps of the monolayers. (1) U. Zerweck, C. Loppacher, T. Otto, S. Grafström, and L. M. Eng, Phys. Rev. B 71 (2005) 125424.(2) B. Moores, F.Hane, L. M. Eng, Z. Leonenko, Ultramicroscopy, (2010) 110, 708-711.
12:30 PM - **VV9.9
From Contact and Non-Contact High-Speed AFM to the Holo Assembler AFM
Mervyn Miles 1 , Loren Picco 1 , Robert Harniman 1 , Oliver Payton 1 , Massimo Antognozzi 1 , David Engledew 1 , David Carberry 1 , James Grieve 1 , David Phillips 1 , Sriram Subramanian 2 , Miles Padgett 3
1 Physics, University of Bristol, Bristol United Kingdom, 2 Computer Science, University of Bristol, Bristol United Kingdom, 3 Physics and Astronomy, University of Glasgow, Glasgow United Kingdom
Show AbstractHigh-speed AFM is important in materials science as well as for biostructures in following processes occurring on short time scales inaccessible to conventional AFM. We are working on two versions of high-speed force microscopy: one is capable of extremely high imaging rates (> 1000 frames per second) and can image over relatively large areas on samples with relatively large height variations (< 1 μm), and the other is a non-contact version which is more appropriate for studying delicate nanoscale structures and processes. Both are also capable of writing structures, e.g., by electrochemical oxidation, at high-speed. AFM at video rate has allowed us to develop a multitouch highly-intuitive interface to directly interact with the scan area and size.At the same time, we have been developing a holographic optical tweezers capable of assembling micro and nano structures including nanotools based on nanorods which can become independent AFM probes controlled and scanned by the holographic optical traps and capable of operating with 4π degrees of freedom (see http://HoloAssembler.com).
VV10/SS8: Joint Session: High Speed and High Resolution Imaging: SPM and Electron Microscopy
Session Chairs
Flemming Besenbacher
Joost Frenken
Thursday PM, December 02, 2010
Fairfax A/B (Sheraton)
2:45 PM - **VV10.1/SS8.1
Catalytic Model Systems Studied by High-resolution, Video-rate in situ Scanning Tunneling Microscopy.
Flemming Besenbacher 1
1 Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus Denmark
Show AbstractTo realize the vision of a clean society and our vision of plentiful, low cost sustainable energy, research and innovation within the area of the rapidly expanding fields of nanoscience and nanotechnology, multi-disciplinary by nature involving physics, chemistry, biology, molecular biology, is mandatory. 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 contributed substantially to our understanding of the processes involved in especially catalysis. In this talk I will show how Scanning Tunneling Microscopy (STM) can reveal fundamental processes in relation to catalysis, and how we can extract quantitative information on surface diffusion of adatoms and molecules [1-2]; diffusion of vacancies; interstitials and molecules, e.g. water molecules on oxide surfaces [2-3]; sintering and diffusion of nanoclusters on oxide surfaces [4]; diffusion of intermediate species; identification of active sites [5-7] and determination of new nanostructures with novel, catalytic properties from time-resolved, high-resolution STM images/movies (see www.phys.au.dk/spm) [7]. The atomic-scale information obtained may even lead to the design of new and improved catalysts in certain cases [6, 5]. References1.S. Horch et al., Nature 398, 1344 (1999)2.S. Wendt et al., Physical Review Letters 96, 066107 (2006)3.S. Wendt et al. Science 320, 1755 (2008) 4.D. Matthey et al., Science 315, 1692 (2007) 5.J. Kibsgaard et al., JACS, 128, 13950 (2006)6.F. Besenbacher et al., Science 279, 1913 (1998)7.F. Besenbacher et al., Surf. Sci.603, 1325 (2009)
3:15 PM - VV10.2/SS8.2
Real Time Chemical Manipulation and Spectroscopy of Single Carbon Nanotube Functionalized AFM Tips using a Correlated Optical and Atomic Force Microscope.
Ifat Kaplan-Ashiri 1 , Eric Titus 1 , Rachel Shaver 1 , Katherine Willets 1
1 Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, United States
Show AbstractThe coupling of AFM with an optical microscope allows real time studies of nanomaterials and single molecules as they undergo chemical changes or interact with the environment around them. Here we demonstrate the ability of a conjugated AFM and optical microscope to measure the real time Raman response of a single carbon nanotube functionalized AFM tip upon interactions with (1) evanescent laser fields with varying penetration depths, (2) oxidizing agents and (3) noble metal nanoparticles. Multiwalled carbon nanotube functionalized tips were fabricated in FIB/SEM, which is equipped with nano-manipulation system. Next, the nanotube-functionalized tips can be placed in the AFM that is mounted on an optical microscope. The nanotube serves as both a Raman active analyte and as a high-resolution AFM tip. Raman is excited with a 532 nm laser and measured alternately with an avalanche photodiode (APD,photons counts) or with a spectrometer. The Raman signal of a mulitwalled carbon nanotube, while it was tapping on the surface, is observed, allowing a variety of processes to be followed in real time. We are able to probe the penetration depth of the excitation laser by using total internal reflection (TIR) and tuning the angle of incidence. We have also demonstrated a change in the Raman intensity of the carbon nanotube, by performing in-situ AFM chemistry on the tip using nitric acid. Last, we present preliminary results of surface enhanced Raman scattering (SERS) from the carbon nanotube tip as it scans over a silver colloid sample. The enhanced electromagnetic signal is correlated in real time with the topography of the colloids.
3:30 PM - **VV10.3/SS8.3
Seeing Catalysis at Work: Video STM and SXRD under Reaction Conditions.
Joost Frenken 1
1 Leiden Institute of Physics, Leiden University, Leiden, 0, Netherlands
Show AbstractScanning tunneling microscopy (STM) and surface X-ray diffraction (SXRD) are both naturally suited to obtain direct information on the structure and the atomic and molecular processes that occur on the surface of a catalyst while it is active in a chemical reaction under the high temperatures and high pressures typical in catalysis. They are used increasingly to find the ‘true’ nature of (model) catalysts under realistic or semi-realistic combinations of temperatures, pressures and gas compositions.We have developed special purpose instrumentation for both techniques, SXRD [1] and STM [2], the latter now reaching atomic resolution on metal model catalysts under reaction conditions. Results will be shown for the oxidation of CO and the reduction of NO on Pt and Pd surfaces under atmospheric pressures at elevated temperatures [2-5]. Our STM- and SXRD-movies demonstrate that at high O2 pressures these surfaces all oxidize, the catalyst simultaneously switching between two different reaction mechanisms and the oxide being most reactive. We resolve various ultrathin oxide structures, which only appear under high partial pressures of oxygen and others that are only stable under the simultaneous presence of O2 and CO.The combination of the STM and SXRD results provides a surprising explanation for the self-sustained oscillations in the reaction rate that appear spontaneously for several of these surfaces. The oscillation mechanism identified here involves a novel role for atomic steps in catalysis [6]. [1] R. van Rijn et al., Rev. Sci. Instrum. 81, 014101 (2010).[2] C. Herbschleb et al., in preparation.[3] J.W.M Frenken and B.L.M Hendriksen, MRS Bulletin 32, 1015 (2007).[4] B.L.M Hendriksen and J.W.M Frenken, Phys. Rev. Lett. 89, 046101 (2002).[5] M.D. Ackermann et al., Phys. Rev. Lett. 95, 255505 (2005).[6] B.L.M. Hendriksen et al., Nature Chem., in press.
4:30 PM - **VV10.4/SS8.4
Compositional Imaging of Multicomponent Materials with AFM-based Electric Methods.
Sergei Magonov 1
1 , Agilent Technologies, Chandler, Arizona, United States
Show AbstractAtomic Force Microscopy (AFM) is the widely used characterization method that provides high-resolution surface imaging and access to local mechanical and electromagnetic properties. The AFM capability for studies of materials in different environments is the unique feature not common to other microscopic techniques. Recent instrumental improvements lead to progress in high-resolution imaging and multi-frequency detection in probing of local mechanical and electric behavior. The latter is the basis of compositional imaging of complex materials and high-resolution quantitative mapping of various materials properties. In the paper we will emphasize the use of AFM-based measurements of surface potential and dielectric constant for identification of individual components in heterogeneous materials. Single-pass Kelvin force microscopy (KFM) with frequency modulation detection of electrostatic forces offers the most precise detection of surface potential with nm-scale spatial resolution. This technique can be applied to a broad range of materials (metals, semiconductors, organic samples, polymers, biological specimen. When KFM is applied in the intermittent contact it allows examining samples in high humidity and vapors of organic solvents (methanol, benzene, toluene, etc). The KFM value will be demonstrated by the results obtained on soldering materials, polymer blends and block copolymers with hydrophilic and fluorinated components, organic self-assemblies, etc. The emphasis will be also made on KFM characterization of materials applied in fuel and solar cells. The local measurements of capacitive derivatives can be interpreted in terms of dielectric constant and its variations. The practical examples taken from studies of organic layers and polymers will demonstrate the use of these studies for compositional imaging. In multi-frequency AFM these studies can be performed simultaneously with KFM. Several aspects of the interplay between theoretical modeling of the AFM-based electric methods and the experiments will be also discussed.
5:00 PM - VV10.5/SS8.5
Imaging of Subsurface Nanostructures via Beam-exit Cross-sectional Ar Ion Polishing (BEXIP) and Ultrasonic Force Microscopy.
Ilya Grishin 1 , Peter Carrington 1 , Viktor Soloviev 2 1 , Robert Jones 1 , Oleg Kolosov 1
1 Physics, Lancaster University, Lancaster, Lancashire, United Kingdom, 2 , Ioffe Physico-Technical Institute, St. Petersburg Russian Federation
Show AbstractScanning probe microscopy (SPM) is well known for its superb nanoscale resolution and sensitivity to surface properties, but it cannot be directly applied to subsurface imaging of nanostructures due to the very nature of the proximity probe imaging. An alternative is to cross-section the sample and expose underlying structures to SPM, as in cross-sectional scanning tunnelling microscopy (X-STM). Unfortunately X-STM needs crystalline cleavage planes and cannot be used for non-crystalline materials. Ion milling (e.g. focused ion beam or FIB) [1] and Ar ion cross-section polishing [2] are other candidate methods. FIB is relatively slow and creates artefacts due to ion implantation into the sample. Ar ion polishing uses an Ar+ beam directed towards the sample surface and a shield plate at 90°, milling the unshielded part of the sample at a high rate and producing a nanoscale smooth macroscopic cross-section perpendicular to the plane of the shield plate. The down side of this method is that there is a “dead zone” of few micrometers near sample surface where the surface quality is low, in the very region of interest for most semiconductor and nanostructures applications.In this paper we present a novel method of using Ar ion beam polishing for SPM subsurface studies that deploy polishing of the area of interest by the ion beam exiting the sample. In order to achieve this, the studied surface is tilted slightly (e.g. 5-10 deg) with respect to the axis of the polishing beam (formed by the shield) that enters from the edge of the sample and underneath the surface of interest (e.g. 20-40 um below the surface) and exits this surface at a glancing angle producing an almost perfect nanoscopically flat surface [3]. In addition, close to open angle ridge profile of the ion beam polished and pristine surfaces does not adversely affect SPM scanning.We applied this novel BEXIP method to the cross-sectioning of a InSb/InAs quantum dot stack layered structure (11 layers of 20 nm thickness per layer) with a thin 5 nm InAs cap on top , milled at a glancing 4° angle. The layers were subsequently visualized with standard SPM as well as Ultrasonic Force Microscopy (UFM) known to be sensitive to local composition via sensitivity to the local elastic moduli. The topography of the surface had nanometre flatness (measured by contact and tapping SPM), whereas the UFM signal provided the data that highlighted the differences on the top 2 of the total 11 layers of quantum dots. We also report successful application of this method to SPM subsurface imaging of VLSI interconnects, thermal oxide layers on semiconductors and porous Si layers and discuss the new method's application to phase change memories, as well as linked challenges and limitations.[1] S. Rubanov, P. R. Munroe, Micron 35(7), 549-556 (2004)[2] H. Takahashi, et al., Microchim Acta 155, 295–300 (2006) [3] O. Kolosov, I. Grishin, UK patent application No 1002645.8 (17 Feb. 2010)
5:15 PM - VV10.6/SS8.6
Transparent Combination of SEMs and FIBs with Online Scanned Probe Microscopy for Device Characterization.
Aaron Lewis 1 , Andrey Ignatov 2 , Anatoly Komissar 2 , Eran Maayan 2 , Hesham Taha 2 , David Lewis 2
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
Show AbstractScanning electron microscopy (SEM) is a moving force in the nanotechnological revolution. Focused ion beam microscopes (FIB) have also become a powerful nanotechnology tool. Scanning probe microscope (SPM) is another enabling technology in this growing field. We have focused on integrated microscopic solutions that have now been able to fully and transparently integrate these worlds of SPM with SEM and FIB. This integrationhas added to electron and ion beam microscopes the possibilities of nanomechanical measurements and imaging, nanoelectrical and nanothermal probing and nano-optical imaging. A special vacuum compatible SPM head and associated probes will be described. This combination permits a geometry for the SPM that allows for free electron and ion beam optical axes. Examples will be shown of these new exciting combinations that enhance electron and ion beam functionality with SPM probing. Such enhancements can be used not only for synergetic imaging but also for excitation and investigation of functional probing of devices and systems.