Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Z27: Advances in Instrumentation and Measurement II |
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Sponsoring Units: GIMS Chair: Charles Agosta, Clark University Room: 329 |
Friday, March 20, 2009 11:15AM - 11:27AM |
Z27.00001: ABSTRACT WITHDRAWN |
Friday, March 20, 2009 11:27AM - 11:39AM |
Z27.00002: Surface Coatings for Gas Detection via Porous Silicon Serdar Ozdemir, Ji-Guang Li, James Gole Nanopore covered microporous silicon interfaces have been formed via an electrochemical etch for gas sensor applications. Rapid reversible and sensitive gas sensors have been fabricated. The fabricated porous silicon (PS) gas sensors display the advantages of operation at room temperature as well as at a single, readily accessible temperature with an insensitivity to temperature drift; operation in a heat-sunk configuration, ease of coating with gas-selective materials; low cost of fabrication and operation, and the ability to rapidly assess false positives by operating the sensor in a pulsed mode. The PS surface has been modified with unique coatings on the basis of a general theory in order to achieve maximum sensitivity and selectivity. Sensing of NH$_{3}$, NO$_{x}$ and PH$_{3}$ at or below the ppm level have been observed. A typical PS nanostructure coated microstructured hybrid configuration when coated with tin oxide (NO$_{x}$, CO) and gold nanostructures (NH$_{3})$ provides a greatly increased sensitivity to the indicated gases. Al$_{2}$O$_{3}$ coating of the porous silicon using atomic layer deposition and its effect on PH$_{3}$ sensing has been investigated. 20-100 nm TiO$_{2}$ nanoparticles have been produced using sol-gel methods to coat PS surfaces and the effects on the selectivity and the sensitivity have been studied. [Preview Abstract] |
Friday, March 20, 2009 11:39AM - 11:51AM |
Z27.00003: Directed-Assembly of Carbon Nanotubes on Soft Substrates for Flexible Biosensor Array Hyoung Woo Lee, Juntae Koh, Byung Yang Lee, Tae Hyun Kim, Joohyung Lee, Seunghun Hong, Mihye Yi , Young Min Jhon We developed a method to selectively assemble and align carbon nanotubes (CNTs) on soft substrates for flexible biosensors. In this strategy, thin oxide layer was deposited on soft substrates via low temperature plasma enhanced chemical vapor deposition, and linker-free assembly process was applied onto the oxide surface where the assembly of carbon nanotubes was guided by methyl-terminated molecular patterns on the oxide surface. The electrical characterization of the fabricated CNT devices exhibited typical p-type gating effect and 1/$f$ noise behavior. The bare oxide regions near CNTs were functionalized with glutamate oxidase to fabricate selective biosensors to detect two forms of glutamate substances existing in different situations: L-glutamic acid, a neuro-transmitting material, and monosodium glutamate, a food additive. [Preview Abstract] |
Friday, March 20, 2009 11:51AM - 12:03PM |
Z27.00004: Mid-infrared Verdet coefficient studies in GaAs, BaF$_2$, and LaSrGaO$_4$, and ZnSe Myoung-Hwan Kim, Volker Kurz, Gheorghe Acbas, Chase Ellis, John Cerne We measure the mid-infrared (wavelength $\lambda$=11 - 0.8 $\mu$m; 0.1 - 1.5 eV) Faraday rotation and ellipticity in GaAs, BaF$_2$, LaSrGaO$_4$, and ZnSe. Since these materials are commonly used as substrates and windows in the mid-infrared, it is important to measure the Faraday signals for background subtraction and to test the accuracy of our measurement techniques. The light sources are lasers and a new custom-modified double-pass prism monochromator with a Xe lamp, which allowed continuous broadband measurements in the 0.31-1.5 eV energy range. Surprisingly, we find reproducible ellipticity signals, even though the radiation is well below the absorption edge of these materials and therefore no circular dichroism is expected. We suggest that the Faraday ellipticity is produced by the static retardance ($R_s$) of the ZnSe photoelastic modulator (PEM), which converts rotation signals into ellipticity. We determine $R_s$ experimentally from the Faraday rotation and ellipticity ratio, produced by either applying a magnetic field or rotating the polarization of light incident on the PEM. Work supported by the Research Corp. Cottrell Scholar Award, NSF-CAREER-DMR0449899, and an instrumentation award from the CAS. [Preview Abstract] |
Friday, March 20, 2009 12:03PM - 12:15PM |
Z27.00005: Diffraction by a Metallic Edge Near Plasma Frequency Miguel A. Alvarez-Cabanillas The behaviors of the fields diffracted by a metallic half-plane near plasma frequency are obtained. Incident plane wave with transverse magnetic polarization TM is diffracted by a gold sheet. The size of the atoms and the interatomic distance in the metallic sheet are assumed to be smaller than the wavelength. The electromagnetic field cannot detect the inner structure of the system and thus observes a homogeneous structure of the medium. These justify the use of a semi-classic theory and quantum effects will not be included. In this limit, the permittivity and the permeability are valid concepts. Finite difference time domain FDTD approach is applied to solve the Maxwell equations, PML as absorbing boundary conditions and a conductor as gold for the half-plane diffractor. Auxiliary Differential Equation method ADE is implemented in the FDTD to consider the nonlinear dispersion behavior of the metallic sheet near the plasma frequency. As results, the diffraction behavior near the plasma frequency by the wave-electron effect is shown; as the dependence of the diffracted fields with the longitude of the thickness of the metallic half-plane. [Preview Abstract] |
Friday, March 20, 2009 12:15PM - 12:27PM |
Z27.00006: ABSTRACT WITHDRAWN |
Friday, March 20, 2009 12:27PM - 12:39PM |
Z27.00007: Fabrication of directional sound sensor by silicon micromachining Michael Touse, Jeffrey Catterlin, Jose Sinibaldi, Gamani Karunasiri A directional sound sensor based on the operational principle of the Ormia ochracea fly's hearing organism [1] was fabricated using micro-electromechanical system (MEMS) technology. The fly uses coupled bars hinged at the center to achieve directional sound sensing by monitoring the difference in their vibration amplitudes. The MEMS design employed in this work consisted of a 1x2 square millimeter polysilicon membrane hinged at the center and positioned about 1 micrometer above the substrate using a sacrificial silicon dioxide layer. Finite element analysis of the device shows two primary vibrational mode frequencies, one corresponding to a rocking mode which is highly dependent on angle of incidence, and the other to a bending motion which remains constant through all angles. Using a laser vibrometer to measure response, rocking and bending modes were observed at driving frequencies of 3.0 and 11.4 kHz, respectively, and angular dependence was in close agreement with modeling. [1] R.N. Miles, R. Robert, and R. R. Hoy, ``Mechanically coupled ears for directional hearing in the parasitoid fly Ormia ochracea,'' J. Acoust. Soc. Am., \textbf{98} (6), Dec. 1995 [Preview Abstract] |
Friday, March 20, 2009 12:39PM - 12:51PM |
Z27.00008: The OSL dating behavior of Martian sediment analogue materials exposed to a simulated Martian solar spectrum Marissa Detschel, Ken Lepper Optically stimulated luminescence dating (OSL) is a terrestrial geochronometric technique being developed for \textit{in-situ} dating of the geomorphic features on the surface of Mars. The solar spectral irradiance reaching the surface of Mars includes ionizing ultraviolet (UV) radiation that does not reach the surface of the Earth. In view of this, an optical system was constructed that closely simulates the Martian solar spectral irradiance, including seasonal variations due to the planet's orbit and attenuation by atmospheric dust. Upon exposure to this simulated environment, the OSL dating behavior of a suite of Martian sediment analogue materials were catalogued. Results suggest that the presence of the additional ionizing UV radiation on the surface of Mars will not compromise optical dating measurements of K- and Ca-feldspars, anhydrite, or hydrous Ca and Mg sulfates. However, Na-feldspar does appear to retain a trapped charge population, which could hinder optical dating of sediments containing more than trace amounts of sodic feldspars. [Preview Abstract] |
Friday, March 20, 2009 12:51PM - 1:03PM |
Z27.00009: ABSTRACT WITHDRAWN |
Friday, March 20, 2009 1:03PM - 1:15PM |
Z27.00010: Variable temperature measurements in cryogenic probe stations; Measurements with Magnetic Fields Jeffrey Lindemuth Electrical and magnetic property measurements of nanoscale materials are important for characterization and understanding of materials and devices. Equally important is to measure these properties at various temperatures. These measurements are facilitated with cryogenic probe stations that provide a variable temperature environment over a wide range of temperatures. However, until this time a major inconvenience was caused by the thermal expansion of the probe tips and probe station as the temperature changed. To prevent the tip movement from damaging the sample, the normal procedure is to lift the probe tips as the temperature changes. This prevents the implementation of totally automated variable temperature measurements. We present results using a new probe design that allows the probe tips to remain in contact to sample during temperature changes. With this new design we demonstrate, with optical microscopy, the total tip movement of less than 2 microns when the temperature of the sample changes from 4.2K to 300K. The same probes that eliminate the movement from thermal expansion also improve the isolation of the measurements to external vibrations. To show the performance of this probe design, variable temperature magnetotransport measurements were preformed. These measurements show that the probe tips do not move with changing temperature and magnetic fields. [Preview Abstract] |
Friday, March 20, 2009 1:15PM - 1:27PM |
Z27.00011: GHz-Bandwidth Signal Processing for Time-Resolved Faraday/Kerr Rotation Experiments Yanjun Ma, Patrick Irvin, Jeremy Levy Faraday/Kerr rotation is a sensitive measurement of the electron spin and its dynamics in semiconductor nanostructures such as GaAs quantum dots. The Kerr rotation angle from a single spin, however, can be as small as $10^{-6}$ rad, which requires massive averaging of the Kerr signal in order to maximize the signal-to-noise ratio. By replacing the mechanical delay line typically found in time resolved Kerr rotation (TRKR) measurements with a continuous wave probe and high-speed electronics, the signal and noise can be sampled more often which results in a higher SNR. However, real-time methods for data collection are typically limited by available memory, resulting in unavoidable dead time for which data cannot be collected and averaged. The approach we have developed integrates a field-programmable gate array (FPGA) with a high-speed digitizer, thus allowing high-speed on-board averaging to overcome these technical limitations. We will demonstrate the performance of this instrument by comparing the results of this system with traditional pump-probe (sampling) techniques and discuss its applicability for a variety of dynamical spin-sensitive experiments in the solid state. [Preview Abstract] |
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