RSS 1.0Faculty Publications-Physics
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Structural and Electronic Properties of Iron-Doped Sodium Montmorillonite Clays: A First-Principles DFT Study
(American Chemical Society, 2019-08)First-principles calculations done via density functional theory were used to study the structural and electronic properties of sodium montmorillonite clay (Mt-Na+) of general formula M x Al3Si8O24H4Na·nH2O (M x : Mg or ... -
Electrical and Optical Characterization of CdTe Solar Cells with CdS and CdSe Buffers: A Comparative Study
(American Institute of Physics, 2018-09)A study is reported comparing the electrical and optical properties of CdTe solar cells, prepared using CdS and CdSe buffer layers, to investigate defects in the bulk and interface, carrier transport, and recombination. ... -
Investigation of Cadmium Telluride Grown by Molecular-Beam Epitaxy using Micro-Raman Spectroscopy Below and Above the Laser Damage Threshold
(American Institute of Physics, 2018-09)The effects of visible laser light on cadmium telluride (CdTe), grown by molecular beam epitaxy, are studied at low (48 µW/µm2) laser power densities using micro-Raman spectroscopy. The Raman spectrum of CdTe shows no ... -
Incomplete Ionization of a 110 meV Unintentional Donor in β-Ga2O3 and its Effect on Power Devices
(Nature Research, 2017-10)Understanding the origin of unintentional doping in Ga2O3 is key to increasing breakdown voltages of Ga2O3 based power devices. Therefore, transport and capacitance spectroscopy studies have been performed to better ... -
Continuous Tuning of W-doped VO2 Optical Properties for Terahertz Analog Applications
(American Institute of Physics, 2014-11-17)Vanadium dioxide (VO2), with its characteristic metal-insulator phase transition, is a prospective active candidate to realize tunable optical devices operating at terahertz (THz) frequencies. However, the abrupt phase ... -
Factors Influencing Photoluminescence and Photocarrier Lifetime in CdSeTe/CdMgTe Double Heterostructures
(American Institute of Physics, 2016-10-28)CdSeTe/CdMgTe double heterostructures were produced with both n-type and unintentionally doped absorber layers. Measurements of the dependence of photoluminescence intensity on excita- tion intensity were carried out, as ... -
Effect of Tb3+ Concentration on the Optical and Vibrational Properties of YBO3 Tri-doped with Eu3+, Ce3+, and Tb3+
(American Institute of Physics, 2014-05-09)Structural and optical studies are reported of yttrium orthoborate YBO3 when tri-doped with Eu3þ, Ce3þ, and Tb3þ, focusing on the role of terbium concentration. Incorporation of Tb3þ affects emission properties for ... -
Optical Studies of the Effect of Oxidation on GaN
(American Vacuum Society, 2014-01-09)Optical studies are reported of GaN following oxide layer growth using thermal oxidation and atomic layer deposition (ALD). The low-temperature photoluminescence (PL) probes the topmost GaN layer (<100 nm) where any influence ... -
Straightforward Electrical Measurement of Forward-voltage to Investigate Thermal Effects in InGaN/GaN High-brightness Light-emitting Diodes
(American Vacuum Society, 2014-11-12)The junction temperature of InGaN/GaN MQW high-brightness light-emitting diodes is measured using an electrical method based on the dependence of diode forward voltage, Vf , on the junction temperature Tj. Electroluminescence ... -
Hydrogen-doping Stabilized Metallic VO2 (R) Thin Films and their Application to Suppress Fabry-Perot Resonances in the Terahertz Regime
(American Institute of Physics, 2014-06-16)We demonstrate that catalyst-assisted hydrogen spillover doping of VO2 thin films significantly alters the metal-insulator transition characteristics and stabilizes the metallic rutile phase at room temperature. With ... -
Radiative and Interfacial Recombination in CdTe Heterostructures
(American Institute of Physics, 2014-12-02)Double heterostructures (DH) were produced consisting of a CdTe film between two wide band gap barriers of CdMgTe alloy. A combined method was developed to quantify radiative and non- radiative recombination rates by ... -
Raman Measurements of Substrate Temperature in a Molecular Beam Epitaxy Growth Chamber
(American Institute of Physics, 2015-01-16)A method is described for directly measuring the temperature of a substrate in a molecular-beam epitaxy (MBE) growth system. The approach relies on the establishment of the temperature depen- dence of Raman-active phonons ... -
Participation and Performance on Paper- and Computer-based Low-stakes Assessments
(Springer Open, 2018-05)Background: High-stakes assessments, such the Graduate Records Examination, have transitioned from paper to computer administration. Low-stakes research-based assessments (RBAs), such as the Force Concept Inventory, ...
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Near-Ultraviolet Micro-Raman Study of Diamond Grown on GaN
(AIP Publishing, 2016-01-19)Ultraviolet (UV) micro-Raman measurements are reported of diamond grown on GaN using chemical vapor deposition. UV excitation permits simultaneous investigation of the diamond (D) and disordered carbon (DC) comprising the ... -
Ultraviolet Micro-Raman Spectroscopy Stress Mapping of a 75-mm GaN-on-Diamond Wafer
(AIP Publishing, 2016-05-23)Full-wafer stress mapping is accomplished using visible and ultraviolet (UV) micro-Raman spectroscopy of a 730-nm thick GaN layer integrated with diamond grown by chemical vapor deposition. The UV measurements taken from ... -
Ultraviolet Micro-Raman Stress Map of Polycrystalline Diamond Grown Selectivity on Silicon Substrates Using Chemical Vapor Deposition
(AIP Publishing, 2018-05-03)Polycrystalline diamond stripes, with a nominal thickness of ∼1.5 μm and various widths, were selectively grown on silicon substrates using chemical vapor deposition. Stress measurements using ultraviolet micro-Raman mapping ... -
Challenges of Contact Module Integration for GaN-based Devices in a Si-CMOS Environment
(AIP Publishing, 2014-05-23)The authors report on the integration of an Au-free contact module intended for AlGaN/GaN high-electron-mobility transistors fabricated in a 200 mm Si complementary metal–oxide–semiconductor facility. Contacts are characterized ... -
Energy Tracking Diagrams
(American Association of Physics Teachers, 2016-02)Energy is a crosscutting concept in science and features prominently in national science education documents. In the Next Generation Science Standards, the primary conceptual learning goal is for learners to conserve energy ... -
Becoming Physics People: Development of Integrated Physics Identity through the Learning Assistant Experience
(American Physical Society, 2016-02-22)[This paper is part of the Focused Collection on Preparing and Supporting University Physics Educators.] In this study, we analyze the experience of students in the Physics Learning Assistant (LA) program at Texas State ... -
Geometric Reasoning about Damped and Forced Harmonic Motion in the Complex Plane
(American Association of Physics Teachers, 2015-09)Complex-valued functions are commonly used to solve differential equations for one-dimensional motion of a harmonic oscillator with linear damping, a sinusoidal driving force, or both. However, the usual approach treats ...
