Papers

AVS2005 Session AS+BI+NS-MoM: Nanoscale Analysis: Biomaterial and Other Applications

Monday, October 31, 2005 8:20 AM in Room 206

Monday Morning

Start	Invited?	Item
8:20 AM		AS+BI+NS-MoM-1 The Development of NSOM for Live Cell Applications R.C. Dunn, O. Mooren (University of Kansas) Near-field scanning optical microscopy (NSOM) is a scanning probe technique that enables optical measurements to be conducted with nanometric spatial resolution. This technique offers single molecule detection limits, high spatial resolution, and simultaneous force and optical mapping of sample properties. As such, it has found applications in many areas including the study of thin films, polymers, and solid-state materials. Perhaps its greatest potential, however, lies in the biological sciences, where fluorescence techniques are well developed for tagging specific proteins or structures or following dynamic processes such as calcium signaling. To date, NSOM measurements on viable cells remains problematic due to the forces involved in maintaining the tip close to the sample. Our laboratory has been actively developing new methods for conducting NSOM measurements that are amenable with soft and fragile samples such as living cells. We recently reported a new NSOM tip design built around a conventional atomic force microscopy tip that can be used to make high resolution fluorescence measurements on living cells. The development of these techniques and their application to the study of lipid rafts and nuclear pore complexes in the nuclear envelope will be discussed.
9:00 AM		AS+BI+NS-MoM-3 Local Mobility in Membranes: Atomic Force Microscopy and Fluorescence Correlation Spectroscopy A.R. Burns, D.J. Frankel (Sandia National Laboratories) The lateral organization and dynamics of lipids and proteins in membranes are critical to cellular signaling processes. Fluorescence imaging and atomic force microscopy (AFM) are both effective ways to map the location and structure of membrane components and domains (e.g., lipid rafts) in supported membranes. Since dynamical processes like translational diffusion of lipids and proteins are dependent on the local membrane structure and molecular interactions, it would be advantageous to correlate dynamics with detailed topography mapped out with AFM. We do this by performing fluorescence correlation spectroscopy (FCS) at specific sites imaged by simultaneous AFM and submicron confocal fluorescence microscopy. We have thus examined the relative partitioning and diffusion coefficients for both tail and head labeled GM1 ganglioside, as well as for head and tail labeled phospholipids, in phase separated domains. Our results indicate significant mobility changes in the micron-scale domains due to differences in lipid packing and ordering. We also observe a large reduction in the mobility of GM1 when bound to cholera toxin B fragments. The effects of membrane proteins will be discussed as well. This research was supported in part by the Division of Materials Science and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy under Contract DE-AC04-94AL85000.
9:20 AM		AS+BI+NS-MoM-4 Molecular Orientation Imaging with sub 10-nm Resolution by Vector Piezoresponse Force Microscopy B.J. Rodriguez (North Carolina State University); S. Jesse, A.P. Baddorf (Oak Ridge National Laboratory); A. Gruverman (North Carolina State University); S.V. Kalinin (Oak Ridge National Laboratory) Functional properties of calcified and connective tissues are determined by the relative ordering and orientation of a relatively small number of biopolymers, such as collagen. Here we present a new approach for local molecular orientation imaging in biological systems by Vector Piezoresponse Force Microscopy (Vector PFM). Vector PFM is capable of determining the local electromechanical activity and orientation in piezoelectric materials with a spatial resolution below 10 nm. The applicability of Vector PFM to biological systems is demonstrated for objects from butterfly wings to bones. Electromechanical characterization of enamel and dentin layers in human tooth is demonstrated. The vector electromechanical response of a bundle of collagen molecules in human tooth dentin has been visualized with 5 nanometer resolution. A method for imaging the local orientation of biomolecules from Vector PFM data has been illustrated using collagen molecules embedded in a hydroxyapatite matrix. As another example, 2D piezoelectric properties and local elasticity of a butterfly wing are measured with nanoscale resolution and interpreted in terms of the relative orientation of chitin molecules in the wing scales. The ubiquitous presence of electro-activity in biopolymers, such as chitin, keratin, collagen, and cellulose, suggests that Vector PFM has exceptional potential for orientation imaging of biological materials on the sub-10 nanometer length scale. Research was sponsored by the U.S. Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC and by the National Science Foundation grant DMR-0072998 (AG). Research partially performed as a Eugene P. Wigner Fellow (SVK).
9:40 AM		AS+BI+NS-MoM-5 Nanoscale Raman and Fluorescence Microscopy of Carbon Nanotubes A. Hartschuh, H. Qian, A.J. Meixner (University of Tuebingen, Germany); N. Anderson, L. Novotny (University of Rochester) Spectroscopic methods with high spatial resolution are essential for understanding the physical and chemical properties of nanoscale materials including biological proteins, quantum structures and nanocomposite materials. Optical techniques are of special interest because the energy of light quanta is in the range of electronic and vibrational transitions. Advances in near-field optics open up new means to overcome the diffraction limit and extend the range of optical measurements to the length scales of most nanosystems. Recently, a near-field optical technique based on local field enhancement has been demonstrated which allows to perform spectroscopic measurements with 20 nm spatial resolution.^1,2 The method makes use of the strongly enhanced electric field close to a sharp metal tip under laser illumination. In this approach the metal tip is held a few nanometers above the sample surface so that a highly localized interaction between the enhanced field and the sample is achieved. Raster scanning the sample then allows for simultaneous optical and topographic imaging. Single-walled carbon nanotubes (SWCNTs) have been the focus of intense interest due to a large variety of potential nanotechnological applications. We demonstrate near-field Raman and fluorescence imaging of the same individual single-walled carbon nanotube and show that a spatial resolution of less than 20 nm can be achieved. The high-resolution capability and chemical specificity of the presented method is used to study local variations in the optical spectra of SWCNTs which would be hidden in farfield measurements. The technique has great potential for becoming a routine tool for the chemical analysis of surfaces at high spatial resolution. ¹ E. J. Sanchez et. al, Phys. Rev. Lett. 82, 4014 (1999). ² A. Hartschuh et. al, Phys. Rev. Lett. 90, 095503 (2003).
10:20 AM		AS+BI+NS-MoM-7 Scanning Atom Probe Study of Fragmentation of Organic Molecules O. Nishikawa, M. Taniguchi (Kanazawa Institute of Technology, Japan) Fragmentation of two organic molecules, crystal violet [(C₂₅N₃H₃₀)⁺Cl^-: 408 amu] and tetra-n-butyl-ammonium hydroxide [N(C₄H₉)₄⁺OH^-: 259 amu], was studied at atomic level by mass analyzing the dissociated fragments with the scanning atom probe (SAP). In the SAP analysis the molecules and their fragments are field evaporated as positive ions and detected one by one. Since the field evaporation is a static process, it does not disorder surface structure breaking atomic bonds by external energy. Accordingly, evaporated positive ions reflect the binding state in the molecules. For example, the radical of polythiophene, SC₄H₂, is field evaporated as doubly charged ions indicating that the atoms forming the radical are strongly bound. A thin layer of crystal violet was deposited on a tungsten substrate. Since the crystal violet is non conductive, the molecules are field evaporated applying a DC high voltage to the tungsten substrate and irradiating the specimen with a pulsed laser beam, 2nd harmonic of YAG laser, 532 nm. Although non-dissociated molecule ions are detected, most molecules are dissociated showing the ions such as C₁₃H₂, C₁₃NH₄ and C₈NH_n. The detected fragments suggest that no double bonds are broken. When the molecule layer was deposited on a titanium oxide layer, all molecules were dissociated possibly due to the photo-catalytic function of titanium oxide. The most abundant fragment is C₄NH_n. The ratio of the number of carbon atoms to that of nitrogen atom was found to be nearly 8:1 as expected. Although the dissociation of tetra-n-butyl-ammonium hydroxide molecules at the boundary with the tungsten substrate is noticeable, the dissociation is insignificant at non-boundary areas. It was also found that hydroxide of the molecules is dissociated and oxygen atoms are bound with tungsten. This may suggest that tungsten also have catalytic function.
10:40 AM		AS+BI+NS-MoM-8 Surface Potential Mapping of DNA-protein Complex at Molecular Level E. Mikamo, F. Yamada, T. Matsumoto, T. Kawai (Osaka University, Japan) Atomic force microscopy (AFM) is a valuable method for the study of biomolecules such as DNA, RNA and proteins at real-space. The biomolecules have generally been adsorbed on the insulating substrate as mica to observe by AFM. However, it is very hard to measure the local electric properties of the insulating substrate and the conductive substrate has been commonly used. Recently our group demonstrated the measurement of electric properties of DNA and Au nanoparticles on mica and sapphire substrate. This result encouraged us to measure the complex of biomolecules on the insulating substrate at molecular level. We report here surface potential and capacitance measurement of DNA, protein and DNA-protein complex on the insulating substrate. The experiments are based on frequency mode non-contact AFM (FM-ncAFM). The FM-ncAFM is able to detect the high-sensitive local electrostatic forces and prevent the charge injection caused by tip-sample contact. We observed the surface potential mapping and topographic image simultaneously. The topographic images clearly showed DNA and protein as line and dot structure. The surface potential of corresponded structures is observed as bright contrast. Our results indicate that surface potential of DNA, protein and DNA-protein complex is higher than insulating substrate surface. The potential images resolve the double strand DNA, thin structure less than 2 nm, and protein at single molecular revel. To estimate the capacitance of individual molecules, we measured d(ΔF) per dV images. The measurement of surface potential and capacitance indicate that this technique is able to discriminate the individual molecules on an insulating substrate. This work was supported by grants from the New Energy and Industrial Technology Development Organization (NEDO).
11:00 AM		AS+BI+NS-MoM-9 The Importance of Aberration Corrected SEM and TEM to the Semiconductor Industry A.C. Diebold (SEMATECH & AMRC); B. Foran (ATDF & AMRC); M.J. Yacaman, B.A. Korgel (University of Texas & AMRC) Microscopy continues to be a critical need for the semiconductor industry. Feature sizes continue to shrink with logic having a two-year cycle for introduction of each new technology generation. Over the next fifteen years, the gate length of transistors will rapidly shrink to less than 10 nm. The interconnect technology connecting the transistors will keep pace with this size reduction. Research and development needs occur well ahead of manufacturing needs. Thus, there already is a need for microscopy capable of imaging and characterizing the interfaces, film layers and structures for future devices. Recent advances in electron optics technology have corrected for chromatic and spherical aberrations that have long limited resolution in scanning electron microscopy (SEM) and tranmission electron microscopy (TEM). Commercially available advances include monochromators to reduce the energy spread of the electron source and lens correctors to reduce spherical aberration. Resolution of state of the art scanning TEM and High resolution TEM has been proven below 0.1 nm. Aberration correction technology is also now commercially available for SEM and allowing resolution to 0.6 nm. In this paper we discuss the advances in imaging that aberration corrected lenses have enabled along with semiconductor industry applications. We will discuss near-term applications such as the characterization of interfaces in the transistor gate stack and measurement of strain in the transistor channel, and then also discuss long-term research applications such as nanowires and nanodots. Abberation correction will not solve all microscopy problems, and we will discuss specific cases such as sample or analytical limitations that can obviate any benefit of aberration correction technology.
11:40 AM		AS+BI+NS-MoM-11 Scanning Tunneling Microscope Assisted with Inner-Shell Excitation by Hard X-ray Micro-Beam A. Saito (Riken Harima Inst., Japan); J. Maruyama, K. Manabe (Osaka Univ., Japan); K. Kitamoto (Riken Harima Inst., Japan); K. Takahashi (Osaka Univ., Japan); Y. Tanaka (Riken Harima Inst., Japan); M. Yabashi, M. Ishii (Japan Synchrotron Radiation Res. Inst.); M. Akai-Kasaya (Osaka Univ., Japan); S. Shin, T. Ishikawa (Riken Harima Inst., Japan); Y. Kuwahara, M. Aono (Osaka Univ., Japan) A scanning tunneling microscope (STM) system was developed for in-situ experiments under the irradiation of highly brilliant hard x-rays of synchrotron radiation (SR). It appears attractive to excite the core electrons of specific level under the STM observation, because it may enable to analyze the elements or control the local reaction with the spatial resolution of STM. To surmount a small probability of the core-excitation by hard X-rays, SR of the highest brilliance at the SPring-8 was used. To prevail the difficulties produced by the highly brilliant SR (damage around the STM scanner, thermal and electrical noise, and instability of the system such as thermal drift), the beam size was limited to φ10 µm. The small beam size serves also to obtain a high signal to noise ratio and high spatial resolution by restraining the electrons emitted from a wide area. The in-situ STM observation was enabled by developing an accurate "three-body (invisible micro-beam, tip-end, and sample surface)" alignment system in ultrahigh vacuum. Despite a noisy condition of SR facility and radiation load around the probe tip, STM images were successfully obtained with atomic resolution. The analysis of the clean Si(111) surface revealed that the thermal expansion affects to the behavior of the tip much strongly than reported in the past reports. Next, the tip-current spectra were obtained on Ge nano-islands on the clean Si(111) surface, by changing the incident photon energy across the Ge absorption edge. A current modification was detected at the absorption edge, with a spatial resolution of the order of 10 nm. This system will serve to observation or manipulation with atomic resolution, which is based on the interaction between the surface atoms and the hard X-ray photons.