Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session W10: Focus Session: Surfaces and Interfaces in Electronic Materials IV |
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Sponsoring Units: DCP Chair: Shaowei Chen, University of California, Santa Cruz Room: Baltimore Convention Center 302 |
Thursday, March 16, 2006 2:30PM - 3:06PM |
W10.00001: Synthesizing Metal Nanowires that Detect Molecules Invited Speaker: Noble metal nanowires have attributes including strength, ductility, and chemical stability, that make them attractive candidates for chemical sensing applications. However, in contrast to semiconductor nanowires, the conductivity of metal nanowires is not expected to be responsive to ``charge gating'' induced by the presence at the surface of the nanowire of bound ions. Consequently the properties of metal nanowires for chemical sensing have not been explored. We have developed a new method for preparing arrays of noble metal nanowires that involves the electrodeposition of metals (palladium, silver, platinum and gold) onto stepped graphite surfaces. Under the conditions employed for nanowire growth, metal is deposited selectively at step edges on the graphite surface leading to the formation of polycrystalline nanowires that are up to 1 mm in length and 30-500 nm in diameter. These nanowires adhere weakly to the graphite surface, and arrays of hundreds of wires may be transferred onto glass surfaces using a simple embedding process. These transferred nanowires can form the basis for chemical sensors in which the resistance of the nanowire array is modulated by molecules that chemisorb at the surfaces of these metals. Two examples involve palladium nanowires in the presence of hydrogen, and silver nanowires in the presence of amines. For both of these systems, the changes in resistance ($\Delta $R/R$_{o})$ can be 1000{\%} or more, but the mechanism response for the resistance changes are completely different. What is the origin of these enormous and unexpected resistance changes? In this talk, we focus attention on this issue and we discuss the prospects for developing practical chemical sensors based on these novel mechanisms. [Preview Abstract] |
Thursday, March 16, 2006 3:06PM - 3:18PM |
W10.00002: Novel Metallic Surface Arrays for SERS and Surface Forces Experiments Margo Graca, Jeff Turner, Sung Chul Bae, Steve Granick Nanofabrication techniques based on FIB (dual-beam focused ion beam lithography) and utilizing a novel solid masking scheme have produced extended arrays of coinage metal nanostructures on muscovite mica and semiconductor wafers. First, the FIB process is used to drill holes in the mask with various alternative shapes, from circles to squares to triangles. Their size is variable from $<$100nm to many microns, and their spacing and arrangement are also easily varied. These novel structures were used for two emerging applications. First, we demonstrate nanostructured ``forest'' patterns, arranged perpendicular to the solid, with a high aspect ratio in height to cross-section. Alternatively, these new structures were embedded into hollow spaces within the solid substrate, producing a \textit{physically flat} yet \textit{chemically rough} surface capable of electronic field enhancement. We demonstrate the ability of these new structures to enhance a Raman (SERS) signal with applications to nano-plasmonics. [Preview Abstract] |
Thursday, March 16, 2006 3:18PM - 3:30PM |
W10.00003: Scattering T-matrix theory for surface enhanced Raman scattering in clusters of nanoscale metal particles Karamjeet Arya Very large enhancements up to 14 orders of magnitude in the Raman cross-section from a molecule adsorbed on a single cluster of a few nanaoscale metal particles has been reported recently. The enhancement is believed mainly due to the enhanced electric field because of the excitation of the localized surface plasmon modes. We have developed a Green's function theory using scattering t-matrix approach in the wave-vector space to solve the Maxwell equations for the enhanced field near a metal particle cluster. The large enhancement in the field is due to the multiple scattering of the local modes of the individual metal particles that has been included exactly. We have considered clusters of different shape and size, for example, clusters of two, three, or four spherical particles forming a liner chain, a triangle or a square. Examples of clusters formed on the glass and metal plates are also discussed. We find the enhancement in the Raman cross section can reach up to 10 orders of magnitude for silver particle clusters and is in a broad frequency range. The results for gold particle clusters are also presented. [Preview Abstract] |
Thursday, March 16, 2006 3:30PM - 4:06PM |
W10.00004: Ordered Pore Arrays in Arrays in Alumina: Fabrication and Application Issues Invited Speaker: Ordered two-dimensional arrays of nanopores in alumina have become a popular model system in nanotechnology because of its ease of fabrication and versatility in terms of geometrical parameters and of using it as template for a variety of materials. The presentation will cover the original two-step approach by Masuda published in Science in 1995 for selfordered pore arrays without long range order as well as nanoimprint and interference lithography approaches for long range ordered pore arrays. Guided self-assembly will also be covered. Metal filling of the pores by electrochemical deposition methods for magnetic storage applications and wetting of the pores by polymers which allows the fabrication of complex tube structures will be discussed. A novel method to get segmented nanotubes consisting e.g. of various gold and nickel segments will be described. Finally, the potential of atomic layer deposition in combination with porous alumina will be touched upon. [Preview Abstract] |
Thursday, March 16, 2006 4:06PM - 4:18PM |
W10.00005: Fabrication of and application of anodic alumina film with custom-designed nanochannel arrays Nai-Wei Liu, Anindya Datta, Chih-Yi Liu, Cheng-Yi Peng, Huai-Hsien Wang, Shr-Bin Wu, Tsu-Shin Chan, Chen-Feng Hsu, Juen-Kai Wang, Yuh-Lin Wang Among the strategies for growing one-dimensional straight nanostructure such as nanorods and nanowires, a viable approach is to grow the materials into templates with aligned nanochannels. Recently, porous anodic aluminum oxide (AAO) film has become an attractive template material for its self-aligned array of nanochannels. In this work, we have demonstrated, for the first time, a focused ion beam (FIB) direct-write lithographic method for selectively closing part of the channels of an ordered array on an AAO film creates a custom-designed nanochannels array. The initial ordered arrays are fabricated by FIB lithographic guiding techniques while the closure of the nanochannels within certain area is achieved by FIB bombardment of the AAO film. Besides, arrays of Ag-nanoparticles grown on anodic alumina nanochannels with precisely tunable gaps (5-25 nm) are exploited for surface-enhanced Raman spectroscopy. The enhancement becomes significant for gaps below 10 nm and turns dramatic when gaps reach an unprecedented value of 5 nm. The results are quantitatively consistent with theories based on collectively coupled surface plasmon. [Preview Abstract] |
Thursday, March 16, 2006 4:18PM - 4:30PM |
W10.00006: Novel Solid State Fabrication Techniques T. L. Moore, D. R. Hines, E. Gomar-Nadal, E. D. Williams We have electrochemically fabricated high dielectric coatings and nanowires in porous membranes. TEM images showed the nanowires to contain grains of single crystallinity. I-V characteristics of dielectric coatings have been investigated to optimize resistivity for minimum thickness. We will report on transport properties of structures constructed using these novel components. The feasibility of incorporating these electrochemically prepared solid state structures in nanoimprinted pentacene thin-film transistors will be evaluated. [Preview Abstract] |
Thursday, March 16, 2006 4:30PM - 4:42PM |
W10.00007: Confined self-organization of a lattice of surface magic-cluster and its structure determination Hsuan-Hao Chang, Ming-Yu Lai, Yuh-Lin Wang, Ching-Ming Wei The ability to create an ensemble of nanostructures with specific size, shape, and arrangement on particular positions in space is one of the most important issue in the exploration nanoscience and realization nanotechnology. We have been exploring methods to set an initial structure of a substrate surface, which provides desirable constrains to self-organization process and lead to the formation of arrays of nanostructures with identical size and structure. A two dimensional lattice of Ga surface-magic-clusters (SMC), i. e. clusters exhibiting enhanced stability at certain sizes on a particular surface, has created by using the Si(111)-7x7 surface as a confining template. The structure of the individual SMC is determined by a combination of STM, density-functional calculations, and dynamic low energy electron diffraction. The diffraction method is applicable because the SMCs have identical size/structure and form an ordered array with the exact translational symmetry. The unprecedented detailed structure information provided by the diffraction measurement is consistent with direct microscopic imaging and theoretical calculations. [Preview Abstract] |
Thursday, March 16, 2006 4:42PM - 4:54PM |
W10.00008: Reversible adsorption of Au nanoparticles on SiO$_{2}$/Si: an \textit{in situ} ATR-IR study D. Enders, T. Nagao, A. Pucci, T. Nakayama Adsorption and desorption of Au nanoparticles (AuNP) on the (aminopropyl)triethoxysilan (APTES) treated SiO$_{2}$/Si surface was monitored by \textit{in situ} attenuated total reflection (ATR) infrared spectroscopy in combination with a liquid flow cell. With increasing the AuNP coverage at the surface, the absorption by water vibration was increased due to surface enhanced infrared absorption (SEIRA). Repulsive electrostatic forces between the incoming AuNP and the already adsorbed AuNP layer lead to saturation at submonolayer coverage of the surface. We clarified that the adsorption process can be described very well by a diffusion limited first-order Langmuir-kinetics model. Furthermore, we show that the AuNPs desorb from the surface when they are exposed to the solution of aminoethanethiol (AET). [Preview Abstract] |
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