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SSRN 2024年

作者： Emu, Injamamul Hoque Samuels, Brian C. Karmakar, Subrata Hamid, Md. Abdul Shiam, Istiaq Firoz Sarkar, Pallab Kumar Tasnim, Ayesha Haque, Ariful Droopad, Ravi Ingram School of Engineering Texas State University San MarcosTX78666 United States Materials Science Engineering & Commercialization Program Texas State University San MarcosTX78666 United States

High-quality crystalline copper gallate (CuGa2O4) thin films were grown on c-plane sapphire substrates using the pulsed laser deposition (PLD) technique by optimizing the growth parameters (i.e., temperature, oxygen chamber pressure, and laser energy density). The obtained XRD patterns validated that the preferred orientation of the crystalline CuGa2O4 thin film is along the [111] direction, and the crystallinity of the films improved with increasing substrate temperature while maintaining a constant O2 pressure, as assessed by measuring the full width at half maximum (FWHM) of the prominent (222) plane. Reducing the oxygen pressure leads to the emergence of β-Ga2O3 peaks rather than the CuGa2O4 peaks due to the incomplete oxidation of copper (Cu). Subsequent XRD phi (φ) scans revealed a sixfold rotational symmetry of CuGa2O4 and a 30º epitaxial relationship between the film and the sapphire substrate. X-ray photoelectron spectroscopy (XPS) spectra confirmed the presence of Cu1+, Cu2+, and Ga3+ oxidation states in the films. Increasing laser energy density resulted in the complete oxidation of Cu and an increase in the film thickness from 51.8 nm to 183.4 nm. The direct bandgap of CuGa2O4 films was determined to be approximately 4.51±0.01 eV by analyzing the UV-Vis absorbance spectra using the Tauc equation. The refractive index was found to be approximately 2.05±0.01 based on the spectroscopic ellipsometry data. While the impact of increasing laser energy density was negligible on the parameters such as crystal structure, rotational symmetry, oxidation states of gallium (Ga), oxygen (O), bandgap, and refractive index of CuGa2O4 thin film, notable alterations in the oxidation state of Cu and film thickness were observed. © 2024, The Authors. All rights reserved.

关键词： Thin films

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Study of defects in CdTe heterostructures using imaging confocal photoluminescence and photoluminescence intensity measurements

Study of defects in CdTe heterostructures using imaging conf...

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2014 IEEE 40th Photovoltaic Specialist Conference (PVSC)

作者： Craig H. Swartz Odille C. Noriega Pathiraja A. R. D. Jayathilaka Madhavie Edirisooriya Xin-Hao Zhao Michael J. DiNezza Shi Liu Yong-Hang Zhang Thomas H. Myers Materials Science Engineering & Commercialization Program Texas State University San Marcos TX USA Center for Photonics Innovation Tempe AZ USA School of Electrical Computer and Energy Engineering Arizona State University Tempe AZ USA

ISBN: (纸本)9781479943975

Confocal photoluminescence is shown to be a powerful tool for analyzing defect structure in epitaxial CdTe appropriate for photovoltaic applications. Non-radiative defects such as dislocations are easily mapped and quantified. Photoluminescence intensity measurements are shown to be a valuable tool for quantifying interface state density. Very low dislocation density and twin content can be achieved for epitaxial CdTe, and low interface state densities result from using CdMgTe barriers.

关键词： Epitaxial growth Radiative recombination DH-HEMTs Indexes Gallium arsenide Lenses

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Enhancing Sp3 Content in Diamond-Like Carbon Thin Film Electrodes by Pulsed Laser Annealing for Durable Charge Storage Performance

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SSRN 2024年

作者： Karmakar, Subrata Halim, Md Abdul Sultana, Maria Sarkar, Pallab Kumar Emu, Injamamul Hoque Jaimes-Leal, Ana Haque, Ariful Electrical Engineering Ingram School of Engineering Texas State University TX78666 United States Civil Engineering Ingram School of Engineering Texas State University TX78666 United States Materials Science Engineering and Commercialization Program Texas State University TX78666 United States

In this work, diamond-like carbon (DLC) thin film electrodes were grown on Si substrate by pulsed laser deposition (PLD) technique, and the implication of pulsed laser annealing (PLA) treatment on their electrochemical supercapacitor performance was examined by two electrode systems in 1M Na2SO4 electrolyte solutions. The Raman spectra confirm signature of the D and G peaks of pristine DLC film at ~1352 cm-1 (1356 cm-1 after PLA) and 1591 cm-1 (1589 cm-1 after PLA), and appearance of minor T2g (diamond) (1332 cm-1) peaks with an increment of the sp3 content after PLA treatment. The X-ray photoelectron spectroscopy (XPS) spectra were deconvoluted into three different contributions C-C (sp2), C-C (sp3), and C-O, and their sp3 percentages were estimated ~48.6%, and 64.5% before and after annealing. The area under cyclic voltammetry (CV) curve and galvanostatic charging discharging (GCD) performance of PLA-treated DLC film were improved and the highest areal-specific capacitance was obtained to be ~48.25 mF/cm2 for scan rate of 5 mV/s and 36.01 mF/cm2 for current density of 2 mA/cm2, respectively. Excellent charging discharging cyclic stability of PLA treated electrode was observed over 5000 cycles, and Coulombic efficiency and capacitance retention were determined to be ~93.5% and ~97.3%, respectively. © 2024, The Authors. All rights reserved.

关键词： Diamonds

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MECHANICAL, THERMAL, AND MORPHOLOGICAL PROPERTIES' COMPARISON OF 3D PRINTED SURFACE TREATED RAGWEED FIBER REINFORCED BIO-COMPOSITES WITH COMMERCIAL BAMBOO FIBER REINFORCED BIO-COMPOSITE

MECHANICAL, THERMAL, AND MORPHOLOGICAL PROPERTIES' COMPARISO...

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SAMPE 2022 Conference and Exhibition

作者： Panta, Subash Tate, Yash Omer, Liam Mix, Ken Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States Department of Agricultural Sciences Texas State University 601 University Drive San MarcosTX78666 United States Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San MarcosTX78666 United States James Bowie Highschool 4103 W Slaughter Ln AustinTX78749 United States

ISBN: (纸本)9781934551417

Applications of natural fiber-based composites continue to grow in many industries as sustainability and recyclability of products gain popularity. Kenaf, Jute, Coir, and Flax based bio-composites have steadily gained traction as an alternative to synthetic based fiber composites. Giant ragweed (Ambrosia trifida), a common weed, has shown promise as another biological source of fiber for composite reinforcement. Unfortunately, the hydrophilic nature of ragweed is incompatible with most nonpolar polymers leading to weak interfacial adhesion between the fiber and matrix. However, treatment of ragweed fibers post-harvest can alleviate incompatibility, yielding a fiber matrix composite with competitive strength and stiffness. The increasing availability of sustainable composites is crucial as the world continues to distance itself from oil-based products. Therefore, this study will determine the mechanical benefits of using a silane treated ragweed fiber within a polylactic acid (PLA) polymer matrix. The novel composite will be compared to commercially available bio-composites reinforced with bamboo fibers. Mechanical testing will be performed under tensile, and flexural loading. In addition, composites will be examined using scanning electron microscopy (SEM) to determine matrix fiber adhesion and surface effects of silane treatment. Energy Dispersive X-ray Spectroscopy (EDAX) is used to determine the treatments density on the sample surface. The composites coefficient of thermal expansion will be compared using thermomechanical analysis (TMA). Copyright 2022. Used by the Society of the Advancement of Material and Process engineering with permission.

关键词： Surface treatment

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Self-assembled Montmorillonite clay-poly vinyl alcohol nanocomposite as a safe and efficient gas barrier

Results in Materials

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Results in materials 2020年 7卷

作者： Dabbaghianamiri, Maedeh Duraia, El-shazly M. Beall, Gary W. Materials Science Engineering and Commercialization Program Texas State University 78666 TX United States Department of Chemistry and Biochemistry Texas State University 78666 TX United States Physics Department Faculty of Science Suez Canal University Ismailia Egypt

Fabrication of polymer nanocomposite usually requires an extensive high shear mixing and substantial energy input. However, it has been demonstrated that polyvinylpyrrolidone (PVP) and Montmorillonite clay nanoparticles (MMT), will spontaneously form a highly ordered nanocomposite film when applied to a surface utilizing an inkjet printing technique. The as-synthesized nanocomposite prepared by this technique exhibits high barrier properties for oxygen gas. This self-assembly of MMT nanosheets inside the polymer matrix appears to be driven by entropic forces. In this work, an efficient gas barrier based on MMT and polyvinyl alcohol (PVOH) nanocomposite is reported. By adding MMT clay to our PVOH polymer, we solve the problem of sensitivity to humidity observed in pure PVOH films. PVOH is a well-known polymer that exhibits excellent gas barrier properties. However, PVOH is very sensitive to humidity and it must be protected by polymer overcoats such as polypropylene to exclude water. PVOH-MMT nanocomposite prepared in this work solves this problem without the need for polymer overcoating for protection. PVOH and MMT are spontaneously self-assembled into a nanocomposite film that exhibits extremely high oxygen barrier, high transparency, and low sensitivity to humidity which can largely be attributed to constrained polymer effects. © 2020 The Author(s)

关键词： Gas barrier MMT Nanocomposite OTR PVOH

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Why Room Temperature GeSn Lasers Need Carbon

Why Room Temperature GeSn Lasers Need Carbon

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IEEE International Conference on Group IV Photonics

作者： Tuhin Dey Augustus W. Arbogast Qian Meng Shamim Reza Aaron Muhowski Joshua Cooper Rachel S. Goldman Thales Borrely Seth R. Bank Mark A. Wistey Materials Science Engineering and Commercialization Program Texas State University San Marcos Texas USA Department of Physics Texas State University San Marcos Texas USA Department of Electrical and Computer Engineering University of Texas at Austin Austin Texas USA Department of Materials Science and Engineering University of Michigan Ann Arbor MI USA Departments of MSE Physics and EECS University of Michigan Ann Arbor MI USA Department of Physics and MSEC Program Texas State University San Marcos Texas USA

Device models show GeSn lasers are limited by weak electron and photon confinement. Adding carbon offers strong conduction band offsets, freeing SiGeSn layers for separate confinement heterostructures, reducing thresh...

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Heterogeneous Integration of High-Quality Diamond on Aluminum Nitride with High Seeding Density

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SSRN 2022年

作者： Anupam, K.C. Anderson, Jonathan Engdahl, Christopher Piner, Edwin L. Holtz, Mark W. Materials Science Engineering and Commercialization Program Texas State University San MarcosTX78666 United States Crystallume Inc. 3397 De La Cruz Boulevard Santa ClaraCA95054 United States Department of Physics Texas State University San MarcosTX78666 United States

High quality diamond, ~ 10 µm thick, is deposited on AlN/Si by hot filament chemical vapor deposition with low (108 cm-2) and high seeding density (>1012 cm-2). The higher seeding density suppresses three-dimensional growth resulting in films with reduced roughness, improved uniformity, and a more abrupt transition without voids between the diamond and AlN compared to films grown at lower seeding density. Furthermore, micro-Raman results of diamond films grown using higher seeding density show improved quality extending from the substrate to the surface. © 2022, The Authors. All rights reserved.

关键词： Aluminum nitride

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Amphoteric Be in GaN: Experimental Evidence for Switching between Substitutional and Interstitial Lattice Sites

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Physical Review Letters 2017年第19期119卷 196404-196404页

作者： Filip Tuomisto Vera Prozheeva Ilja Makkonen Thomas H. Myers Michal Bockowski Henryk Teisseyre Department of Applied Physics Aalto University P.O. Box 15100 FI-00076 Aalto Espoo Finland Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San Marcos Texas 78666 USA Institute of High Pressure Physics PAS Sokołowska 29/37 01-142 Warsaw Poland Institute of Physics PAS Al. Lotników 32/46 02-668 Warsaw Poland

We show that Be exhibits amphoteric behavior in GaN, involving switching between substitutional and interstitial positions in the lattice. This behavior is observed through the dominance of BeGa in the positron annihilation signals in Be-doped GaN, while the emergence of VGa at high temperatures is a consequence of the Be impurities being driven to interstitial positions. The similarity of this behavior to that found for Na and Li in ZnO suggests that this could be a universal property of light dopants substituting for heavy cations in compound semiconductors.

关键词： Defects Dopants Point defects Vacancies Doped semiconductors III-V semiconductors LEDs Density functional theory Positron annihilation spectroscopy

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Study of Recombination in CdMgTe/CdTeSe Heterostructures Using Photoluminescence Intensity and Lifetime Measurements with Confocal Photoluminescence Microscopy

Study of Recombination in CdMgTe/CdTeSe Heterostructures Usi...

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IEEE Photovoltaic Specialist Conference

作者： C.H. Swartz M. Edirisooriya O.S. Ogedengbe B.L. Hancock S. Sohal E.G LeBlanc P.A.R.D. Jayathilaka O.C. Noriega M. Holtz T.H. Myers K.N. Zaunbrecher Materials Science Engineering & Commercialization Program Texas State University San Marcos TX 78666 USA National Renewable Energy Laboratory 15013 Denver West Parkway MS RSF200 Golden CO 80401 USA

ISBN: (纸本)9781479979455

Intensity-resolved and time-resolved PL are shown to be powerful tools for analyzing recombination in epitaxial CdTe appropriate for photovoltaic applications. Non-radiative defects such as dislocations are easily mapped and quantified by confocal photoluminescence. Very low dislocation density and twin content, as well as very high luminescence efficiency and measured lifetime (450 ns), can be achieved by Se-alloying to lattice match CdTeSe to InSb substrates. Analysis suggests the bulk lifetime for epitaxial CdTeSe is in excess of 700 ns.

关键词： II-VI semiconductor materials Photoluminescence Semiconductor epitaxial layers Lifetime estimation

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Electric Field Emission in GdNiO3 Microflower

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SSRN 2024年

作者： Karmakar, Subrata Parey, Vanshree Mistari, Chetan D. Hamid, Md Abdul Emu, Injamamul Hoque Halim, Md Abdul Sanyal, Gopal Chakraborty, Brahmananda More, M.A. Droopad, Ravi Haque, Ariful Electrical Engineering Ingram School of Engineering Texas State University San MarcosTX78666 United States Institute of Chemical Research of Catalonia The Barcelona Institute of Science and Technology Av. Països Catalans 16 Tarragona43007 Spain Department of Physics Savitribai Phule Pune University Maharashtra Pune411007 India Mechanical Metallurgy Division Bhabha Atomic Research Centre Trombay Mumbai400085 India High Pressure and Synchrotron Radiation Physics Division Bhabha Atomic Research Centre Trombay Mumbai400085 India Homi Bhabha National Institute Anushaktinagar Mumbai400094 India Materials Science Engineering & Commercialization Program Texas State University San MarcosTX78666 United States

GdNiO3 microflowers were synthesized by hydrothermal method with unit sizes of about 2.2-3.5 μm and petal sizes of ~75-100 nm. The X-ray diffraction pattern (XRD) and Raman spectra reveal an orthorhombic crystal structure with the space group Pbnm and various Raman active vibrational modes i.e., Ag, B1g, B2g associated with rare earth nickelates. The total density of states (TDOS) was calculated by density functional theory (DFT) study using a hybrid functional (HSE06) and the volume of TDOS near the Fermi level confirms the semiconducting nature of GdNiO3 with band gap ~0.688 eV. The local bulk work function (φ) was estimated theoretically at ~5.35 eV from DFT calculations which is one of the essential parameters for the field enhancement factor (β). Field emission current density (J) vs. applied electric field (E) divulges a low turn-on field (Eto)~4.6 V/μm@1 μA/cm2 and a threshold field (Eth)~5.2 V/μm@10 μA/cm2 respectively. The Fowler-Nordheim (F-N) model was introduced to calculate β ~1637 and long-term field emission current stability was observed experimentally > 4 h at the preset values of current 2 μA and 10 μA, respectively. The easy preparedness, low turn-on field, and long-term current stability without significant decay suggest this material to be an efficient electron field emitting material in the rare-earth nickelates series. © 2024, The Authors. All rights reserved.

关键词： Rare earths

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