Bulletin of the American Physical Society
2005 Ohio Sections of the APS and AAPT Joint Fall Meeting
Friday–Saturday, October 14–15, 2005; Cleveland, OH
Session D1: Solid State Physics - Experiments |
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Chair: Paul Hambourger Room: Cleveland State University 3 |
Saturday, October 15, 2005 9:30AM - 9:42AM |
D1.00001: A Segmented Aerogel Cherenkov Detector for the HKS Spectrometer Pavlo Baturin, Joerg Reinhold A new hypernuclear spectrometer system has been built by the E01-011 collaboration at Jefferson Lab. This spectrometer system employs a segmented aerogel Cherenkov detector for pion suppression in the trigger. The talk will present the design and performance results from the first data taking run in Summer 2005. [Preview Abstract] |
Saturday, October 15, 2005 9:42AM - 9:54AM |
D1.00002: Micro-characterization of diamond like carbon thin films on glass Jeremy McMinis, Rene Crombez, Eva Montalvo, Weidian Shen Diamond like carbon (DLC) coatings have been used with increasing increasingly in industrial, military, medical, and commercial applications due to their unique mechanical and thermal properties. To investigate the mechanical and tribological properties of a several nanometer thick DLC coating on glass substrate indentation and scratch tests were performed. A Nano-Indenter XP made by MTS equipped with a diamond indenter an a scanning probe microscope, the Nanoscope IIIa, made by Veeco were used to perform the indentation tests. A normal force was applied to a pre-determined maximum load while the displacement into the surface was monitored, resulting in the loading-unloading curves measing displacement as a function of force. Using this data the hardness and elastic modulus of the material can be measured. In the scratch tests the Nano Indenter XP was used to create scratches with an increasing normal load of up to 90mN while the real time displacement of, and lateral force on the tip were recorded. The SPM was then used to measure residual displacement and determine modes of damage along the scratch. Compared to Si$_{3}$N$_{4}$ and ZrO$_{2}$ coated glass, as well as uncoated glass, the DLC coatings showed unique properties which may be attributable to the large compressive stress in the films. [Preview Abstract] |
Saturday, October 15, 2005 9:54AM - 10:06AM |
D1.00003: Electrical conductivity measurements of sputter-deposited Scandium Nitride thin films. Mark Little, Andrew Moore, Matt Koepke The electrical and optical properties of sputter-deposited ScN films on sapphire have been investigated using hall measurement and absorption techniques. Film growth temperature was varied from room temperature to 800$^{\circ}$ C. Sheet resistance is seen to decrease exponentially with increasing growth temperature from $\sim $ 5e11 to 12000 Ohms/square. Sheet carrier density was observed to increase exponentially and while mobility remained relatively constant ($\sim$ 2 cm$^{2}$/Vs) for growth temperatures above 400$^{\circ}$ C. Absorption measurements show an average band gap 2.8 eV with some samples having a distinct increase in adsorption at $\sim$ 4.6 eV. Currently, film composition and structure are being analyzed by RBS and XRD to help determine the nature of the electrical and optical measurements. The results of both investigations will also be presented. [Preview Abstract] |
Saturday, October 15, 2005 10:06AM - 10:18AM |
D1.00004: Optical Analysis of Thin Films for Photovoltaics Technology: Spectroscopic Ellipsometry of Multi-Layer Transparent Conducting Oxide Films Kevin Wells Spectroscopic ellipsometry (SE) is extremely useful in photovoltaics research for determining the optical properties of solar cells from the polarization state change that occurs when polarized light is reflected at an oblique angle from the surface. Tec-15 glass is a commercially produced glass that is coated with transparent conducting oxide layers and is used as a substrate in the production of solar cells. Using various techniques, we have developed a model for the dielectric functions of the layers on Tec-15 glass that leads to an improvement in the quality of the fit to SE data over that provided by previous models. This improvement came primarily from substituting Tauc-Lorentz oscillators for Lorentz oscillators in the previous models. Further analysis found that this model can be further improved in the future through the use of transmittance measurements in addition to the SE measurements. [Preview Abstract] |
Saturday, October 15, 2005 10:18AM - 10:30AM |
D1.00005: Thermally Stable Schottky Contacts on n-type GaN using ZrB${_2}$ Tom Oder, Pamela Martin Zirconium boride Schottky diodes were successfully fabricated on n-type GaN grown by metalorganic chemical vapor deposition. Nickel gallide was used as the ohmic contact and the metal films were deposited by DC magnetron sputtering. The diodes were characterized using current-voltage measurements, optical microscopy and Rutherford backscattering spectroscopy. Barrier height of 0.8 eV was obtained on as-deposited Schottky contacts. The ideality factor was obtained to be 2.2. High temperature stability of these diodes was also investigated using rapid thermal annealing in nitrogen gas for 20 minutes. Our results showed a decrease in barrier height to 0.7 eV after annealing at 300$^{\circ}$C and a further decrease to 0.6 eV after further anneal at 400$^{\circ}$C. However, the barrier height remained at around 0.6 eV even when the diodes were annealed at 600$^{\circ}$C. [Preview Abstract] |
Saturday, October 15, 2005 10:30AM - 10:42AM |
D1.00006: $^{181}$\textit{Ta-}PAC Experiments with Zircon: The Case of the Lost Anisotropy Herbert Jaeger, Sean McBride Perturbed angular correlation spectroscopy (PAC) is a nuclear technique often used to probe the hyperfine interaction of a nuclear moment with extra-nuclear fields. For example the electric field gradient (\textit{EFG}) at a $^{181}$\textit{Ta} probe nucleus in zircon (\textit{ZrSiO}$_{4})$ depends on the positions of the \textit{Zr}, \textit{Si}, and $O$-atoms and is very sensitive to structural rearrangements. In our PAC experiments with zircon we have shown that a very subtle rearrangement of \textit{Si}-atoms within the unit cell leads to a change in the temperature dependence of the \textit{EFG}.$^{1)}$ In addition to the \textit{EFG}, we also measure the anisotropy of the emitted $\gamma \gamma $-cascade in our PAC experiments. The anisotropy is a nuclear property but, because of finite sample and detector size, it also depends somewhat on the geometry of the detector arrangement. However, with a given nucleus and a fixed geometry one would not expect a substantial change in the anisotropy during a series of measurements, say as a function of temperature. Yet our PAC spectra of zircon show a consistent decrease of the anisotropy in the temperature range between 800 and 650$^{\circ}$ C. We will discuss possible reasons for this apparent loss in anisotropy. $^{1) }$H. Jaeger, K. S. Pletzke, and S. P. McBride, \textit{Perturbed Angular Correlation Study of Naturally Occurring Zircon with Very Small Impurity Concentrations}, accepted for publication in Hyperfine Interactions (2005). [Preview Abstract] |
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