Bulletin of the American Physical Society
2009 Joint Spring Meeting of the Ohio Sections of the APS and AAPT
Volume 54, Number 3
Friday–Saturday, April 24–25, 2009; Ada, Ohio
Session C3: Plasma Physics and Semiconductors |
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Chair: Terrence Sheridan, Ohio Nothern University Room: McIntosh Center Ballroom |
Saturday, April 25, 2009 8:16AM - 8:28AM |
C3.00001: Determination of Argon metastable density from relative emission intensity measurements combined with optical emission cross section data Jared Miles, Steven Adams, Adam Laber, Boyd Tolson The plasma diagnostic technique of optical emission spectroscopy can yield a variety of information depending on the resolution of measurement and the extent of supporting data that exists on the fundamental optical properties of the species of interest. Advanced plasma diagnostics can be achieved when optical emission measurements are combined with available electron-impact cross sections, yielding many useful plasma parameters such as electron density, electron temperature, and gas temperature as well as absolute species concentration. In recent years, a considerable amount of data has been compiled for electron excitation of Argon, for which cross-sections have been measured for electron excitation from both the ground state and metastable states. In this work, it was investigated how the different patterns of excitation rates from the Ar ground and metastable states could, under various conditions, yield information on absolute Ar metastable concentrations from simple measurements of relative intensities of spectral lines in the violet range. [Preview Abstract] |
Saturday, April 25, 2009 8:28AM - 8:40AM |
C3.00002: Investigation of 1D to 2D phase transition in small dusty plasma Andrew L. Magyar, T.E. Sheridan We experimentally study a system of $n \le 8$ microscopic dust particles floating in a plasma and confined in a two-dimensional biharmonic potential well as the well anisotropy is varied. When the well is highly anisotropic, the particles lie in a one-dimensional straight configuration. As the anisotropy is decreased, the system undergoes a 1D-2D zigzag transition. The well anisotropy is determined by measuring the center-of-mass frequencies from the particles' Brownian motion. The cluster is characterized by its root-mean-squared (rms) length and width. The transverse size of the cluster $y_{\rm rms}$ is used to characterize the 1D-2D transition. Near the critical point, we find that $y_{\rm rms}$ closely follows a power law, indicating that the transition can be viewed as a continuous phase transition from a 1D to a 2D state, even though the number of particles is small. A second structural transition to an ``elliptical'' state is also observed. The experimental results are in good agreement with a model for particles interacted through a Debye potential and confined in a biharmonic well. [Preview Abstract] |
Saturday, April 25, 2009 8:40AM - 8:52AM |
C3.00003: Theory of two-stream plasma instabilities in graphene Ben Yu-Kuang Hu, Antti-Pekka Jauho We theoretically investigate the possibility of the occurrence of unstable plasma collective modes in graphene (a single layer of carbon atoms in a honeycomb lattice) into which two counter-streaming beams of carriers are injected. The stability of two counter-streaming distributions of carriers is studied by investigating the frequency-dependent dielectric function $\epsilon({\bf q},\omega)$ of the system. We find that the almost perfectly linear electronic dispersion of graphene at the energies in which the beams of carriers are likely to be injected results in instabilities that are qualitatively different from the standard two-stream instabilities for classical plasmas and parabolic-band systems. Specifically, unstable collective modes occur only if the angle that the wavevectors make with respect to the direction of propagation of the counter-streaming carrier beams is larger than a certain critical angle. [Preview Abstract] |
Saturday, April 25, 2009 8:52AM - 9:04AM |
C3.00004: Characterization of WB/SiC Schottky Barrier Diodes Using I-V-T Method James Aldridge, Tom Oder The importance of silicon carbide (SiC) semiconductor for high temperature and high power microelectronic device applications has long been established. We have fabricated SiC Schottky barrier diodes using tungsten boride (WB) as the Schottky contact. The diodes were characterized using the current-voltage-temperature method. The sample was mounted on a heated stage and the temperature varied from about 25 $^{\circ}$C to 300 $^{\circ}$C at intervals of 25 $^{\circ}$C. From the Richardson's plot, we obtained an energy barrier height of 0.96 eV and a Richardson's constant of 71.2 AK$^{-1}$cm$^{-2}$. Using the modified Richardson's plot, we obtained a barrier height of 1.01 eV. From the variation of the ideality factor and the temperature, we determined a characteristic energy of 0.02 eV to 0.04 eV across the range of the measurement temperature. This implies that thermionic emission is dominant in the low measurement temperature range. Our results confirm the excellent thermal stability of WB/SiC Schottky barrier diodes. [Preview Abstract] |
Saturday, April 25, 2009 9:04AM - 9:16AM |
C3.00005: Improved n-type 4H-SiC Schottky Barrier Diodes Using Metal Boride Contacts Rani Kummari, Tom Oder We fabricated Schottky barrier diodes using Schottky contacts of different refractory metal borides deposited at room temperature ($\sim $20$^{\circ}$C) and high temperature (600$^{\circ}$C) on 4H n-type SiC. The borides investigated included W$_{2}$B, W$_{2}$B$_{5}$, WB, CrB$_{2}$, TiB$_{2}$, HfB$_{2}$ and ZrB$_{2}$. The thermal stability of the diodes was tested by annealing using rapid thermal processor (RTP) at 600$^{\circ}$C for 20 minutes in nitrogen. The electrical properties of the diodes were characterized by using current-voltage (I-V) and capacitance-voltage (C-V) measurements before and after the annealing. The physical property of the boride/SiC contact was investigated using Rutherford backscattering spectroscopy (RBS). The diodes with the contacts deposited at 600 $^{\circ}$C had ideality factors around 1.04 -- 1.17, while the diodes with the contacts deposited at room temperature had much larger ideality factors, and in both cases, the barrier heights varied from 0.94 to 1.12 eV. This improvement was traced to the removal of oxygen from the boride/SiC interface. [Preview Abstract] |
Saturday, April 25, 2009 9:16AM - 9:28AM |
C3.00006: Characterization of Epitaxial ZnO Films Grown Using Magnetron Sputtering Tom Oder, Bijayandra Shakya, David Look Zinc oxide has recently gained tremendous interest for the development of a wide range of devices for optoelectronic, electronic and spintronic applications. However, there is still difficulty in obtaining good quality p-type ZnO materials necessary in the development of these devices. We report the results of our studies on ZnO films that were sputter-deposited at 500 $^{\circ}$C on various substrates using different gases. Post-deposition annealing up to 900 $^{\circ}$C in N$_{2}$ resulted in films whose crystalline quality improved with the annealing temperature. Films grown on sapphire in a 1:1 Ar-O$_{2}$ mixture and annealed in N$_{2}$ at 900 $^{\circ}$C for 5 min had the best quality. Low temperature photoluminescence measurements revealed lines from donor-bound excitons and defects in the materials. Blue emissions prominent in O$_{2}$-annealed samples possibly related to Zn-vacancies and their complexes were observed. The two-theta XRD measurements of these films showed a peak at 34.8$^{\circ}$, which corresponds to the diffraction from the (0 0 2) plane of the ZnO and indicates a strong c-axis orientation perpendicular to the surface at the sapphire substrate. [Preview Abstract] |
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