Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session C5: Optical Characterization of Low Dimensional System II |
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Chair: Turi Glinka, West Virginia University Room: Waterfront Hotel Salon F |
Sunday, October 25, 2015 9:36AM - 9:48AM |
C5.00001: The Effect of Gate --Bias Stress and Light illumination on the performance of ZnO Thin-Film Transistors. Prakash Gajurel, Michael Aldridge, Yuri Glinka, Pavel Borisov, Kevin Daly, David Lederman We have investigated the stability of ZnO thin film field effect transistors (TFFTs) grown on Si/SiO$_{\mathrm{2}}$ under the application of positive gate bias stress and light illumination at room temperature. ZnO TFFT devices where a gate voltage is applied over a few seconds are known display a positive shift in the threshold voltage after measurement. This bias stress remains unchanged even if a negative gate voltage stress is applied. Threshold voltage shifts are believed to be a consequence of charge trapping at or near the conducting channel / insulator interface. A negative shift of the transfer curve was achieved exposing the transistor to light in the presence of a small source voltage. The negative shift in threshold voltage depended on the photon energy and exposure time. Our experimental results indicate that the trapped charges responsible for the shift of transfer characteristics are approximately 2.0 eV below the bottom of the ZnO conduction band with an energy distribution width of 3.40 eV. Stressed devices recovered their original characteristics with the photon energy of UV light (365nm, 3.6mW/cm$^{\mathrm{2}})$ within 1818s.This approach could be used to reset stressed TFFTs using light sources. [Preview Abstract] |
Sunday, October 25, 2015 9:48AM - 10:00AM |
C5.00002: Terahertz spectroscopy to explore magnon dynamics in antiferromagnetic MnF2 Derek Bas, Sercan Babakiray, David Lederman, Pavel Borisov, Alan Bristow Antiferromagnetic magnon signatures appear in the terahertz (THz) absorption spectrum of 2-mm bulk Manganese(II) fluoride (MnF2) when cooled below the Neel temperature TN $\approx $ 67 K. Models are used to map the strength and frequency of the magnon as it changes with temperature, and the temporal shift of the THz transient is used to observe the refractive index as thermal expansion and magnetostrictive effects cause it to change. Results of THz spectroscopy, X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID) measurements match known signatures and confirm that the material is pure MnF2. In addition, the UV absorption spectrum reveals a low-temperature D band resonance with a sharp peak at 357 nm. Therefore, by pumping the sample with 357 nm light and simultaneously probing by transmitting a THz source, we propose to excite the magnon directly via the D band and observe its relaxation dynamics' dependence on time and temperature. [Preview Abstract] |
Sunday, October 25, 2015 10:00AM - 10:12AM |
C5.00003: Raman spectroscopic investigation of lithium niobate nanocrystals Keith Veenhuizen, Greg Stone, Bastian Knabe, Karsten Buse, Volkmar Dierolf There is an emerging interest in investigating the properties of ferroelectric materials in confined geometries (nanocrystals, crystal lines in glass, and thin films, for instance). In this work, batches of lithium niobate nanocrystals have been synthesized from various initial ratios of lithium to niobium using the sol-gel method. The batches were analyzed via Raman spectroscopy, SEM imaging, and energy-dispersive X-ray spectroscopy to gain information about particle size, morphology, stoichiometry, and defect content. The nanocrystals are very sensitive to the initial stoichiometric ratio in the synthesis step. It was found that high quality spherical nanocrystals can be synthesized at certain initial stoichiometric ratios. Raman spectra reveal nanocrystal stoichiometry depends on the starting stoichiometry, and the spectra also indicate the nanocrystals have a preferred orientation within the optical trap of the Raman confocal microscope. [Preview Abstract] |
Sunday, October 25, 2015 10:12AM - 10:48AM |
C5.00004: Control of valley pseudospin in two-dimensional MoS2 Invited Speaker: Jie Shan . [Preview Abstract] |
Sunday, October 25, 2015 10:48AM - 11:00AM |
C5.00005: Photon Statistics of Quantum Dot Resonance Fluorescence under the Influence of a Non-Resonant Laser DISHENG CHEN, GARY LANDER, KYLE KROWPMAN, GLENN SOLOMON, EDWARD FLAGG We study the statistical behavior of resonance fluorescence from self-assembled InAs quantum dots (QDs) as a function of the density of free charge carriers introduced by a HeNe laser. Second-order correlation measurements show bunching behavior that changes with HeNe laser power which is absent in HeNe-only excited emission. Resonant photoluminescence excitation spectra indicate that the QD experiences discrete spectral shifts and continuous drift due to changes in the local charge environment. These spectral changes, combined with tunneling of charges from the environment to the QD, provide an explanation of the bunching observed in the correlations. [Preview Abstract] |
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