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  • Structural and Electronic Properties of Iron-Doped Sodium Montmorillonite Clays: A First-Principles DFT Study 

    Ferreira, Camila R.; Pulcinelli, Sandra H.; Scolfaro, Luisa M.; Borges, Pablo D. (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 ...
  • Investigation of Cadmium Telluride Grown by Molecular-Beam Epitaxy using Micro-Raman Spectroscopy Below and Above the Laser Damage Threshold 

    Sohal, Sandeep; Edirisooriya, Madhavie; Myers, Thomas H.; Holtz, Mark (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 ...
  • Electrical and Optical Characterization of CdTe Solar Cells with CdS and CdSe Buffers: A Comparative Study 

    Mia, Md Dalim; Swartz, Craig H.; Paul, Sanjoy; Sohal, Sandeep; Grice, Corey R.; Yan, Yanfa; Holtz, Mark; Li, Jian V. (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. ...
  • Incomplete Ionization of a 110 meV Unintentional Donor in β-Ga2O3 and its Effect on Power Devices 

    Neal, Adam T.; Mou, Shin; Lopez, Roberto; Li, Jian V.; Thomson, Darren B.; Chabak, Kelson D.; Jessen, Gregg H. (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 ...
  • Straightforward Electrical Measurement of Forward-voltage to Investigate Thermal Effects in InGaN/GaN High-brightness Light-emitting Diodes 

    Hancock, Bobby L.; Holtz, Mark (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 ...
  • Raman Measurements of Substrate Temperature in a Molecular Beam Epitaxy Growth Chamber 

    Hutchins, Travis H.; Nazari, Mohammad; Eridisoorya, Madhavie; Myers, T. M.; Holtz, Mark (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 ...
  • Optical Studies of the Effect of Oxidation on GaN 

    Karaoglan-Bebek, Gulten; Woo, Jung Hwan; Nikishin, Sergey; Harris, Harlan Rusty; Holtz, Mark (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 ...
  • Hydrogen-doping Stabilized Metallic VO2 (R) Thin Films and their Application to Suppress Fabry-Perot Resonances in the Terahertz Regime 

    Zhao, Yong; Karaoglan-Bebek, Gulten; Pan, Xuan; Holtz, Mark; Bernussi, Ayrton; Fan, Zhaoyang (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 ...
  • Continuous Tuning of W-doped VO2 Optical Properties for Terahertz Analog Applications 

    Karaoglan-Bebek, Gulten; Hoque, M. N. F.; Holtz, Mark; Fan, Zhaoyang; Bernussi, Ayrton (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 

    Swartz, Craig H.; Zaunbrecher, K. N.; Sohal, Sandeep; LeBlanc, E. G.; Edirisooriya, Madhavie; Ogedengbe, Olanrewaju S.; Petersen, John E.; Jayathilaka, Pathiraja A. R. D.; Myers, Thomas H.; Holtz, Mark; Barnes, T. M. (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+ 

    Sohal, Sandeep; Nazari, Mohammad; Zhang, X.; Hassanzadeh, Ebrahim; Kuryatkov, Vladimir; Chaudhuri, Jharna; Hope-Weeks, Louisa J.; Huang, Juyang; Holtz, Mark (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 ...
  • Radiative and Interfacial Recombination in CdTe Heterostructures 

    Swartz, Craig H.; Edirisooriya, Madhavie; LeBlanc, E. G.; Noriega, O. C.; Jayathilaka, Pathiraja A. R. D.; Ogedengbe, Olanrewaju S.; Hancock, Bobby L.; Holtz, Mark; Myers, Thomas H.; Zaunbrecher, K. N. (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 ...
  • Participation and Performance on Paper- and Computer-based Low-stakes Assessments 

    Nissen, Jayson M.; Jariwala, Manher; Close, Eleanor W.; Van Dusen, Ben (Springer Open, 2018-05-07)
    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, have ...
  • Challenges of Contact Module Integration for GaN-based Devices in a Si-CMOS Environment 

    Johnson, Derek W.; Ravikirthi, Pradhyumna; Suh, Jae Woo; Lee, Rinus T. P.; Hill, Richard J. W.; Wong, Man Hoi; Piner, Edwin L.; Harris, Harlan Rusty (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 ...
  • Near-Ultraviolet Micro-Raman Study of Diamond Grown on GaN 

    Nazari, Mohammad; Hancock, Bobby Logan; Anderson, J.; Savage, A.; Piner, Edwin L.; Graham, S.; Faili, F.; Oh, S.; Francis, D.; Twitchen, D.; Holtz, Mark (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 

    Hancock, Bobby Logan; Nazari, Mohammad; Anderson, J.; Piner, Edwin L.; Faili, F.; Oh, S.; Twitchen, D.; Graham, S.; Holtz, Mark (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 

    Ahmed, Raju; Nazari, Mohammad; Hancock, Bobby Logan; Simpson, J.; Engdahl, C.; Piner, Edwin L.; Holtz, Mark (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 ...
  • Becoming Physics People: Development of Integrated Physics Identity through the Learning Assistant Experience 

    Close, Eleanor W.; Conn, Jessica; Close, Hunter G. (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 

    Close, Hunter G. (American Association of Physics Teachers, 2015-09-01)
    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 ...
  • Energy Tracking Diagrams 

    Scherr, Rachel E.; Harrer, Benedikt W.; Close, Hunter G.; Daane, Abigail R.; DeWater, Lezlie S.; Robertson, Amy D.; Seeley, Lane; Vokos, Stamatis (American Association of Physics Teachers, 2016-02-01)
    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 ...

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