Using The Inelastic Background In Hard X-Ray Photoelectron Spectroscopy For A Depth-Resolved Analysis Of The Cds / Cu(In,Ga)Se < Inf > 2 < / Inf > Interface,
2021
University of Nevada, Las Vegas
Using The Inelastic Background In Hard X-Ray Photoelectron Spectroscopy For A Depth-Resolved Analysis Of The Cds / Cu(In,Ga)Se < Inf > 2 < / Inf > Interface, Dirk Hauschild, Ralph Steininger, Dimitrios Hariskos, Wolfram Witte, Sven Tougaard, Clemens Heske, Lothar Weinhardt
Chemistry and Biochemistry Faculty Research
The inelastic background of hard x-ray photoelectron spectroscopy data is analyzed to paint a depth-resolved picture of the CdS/Cu(In,Ga)Se2 (CdS/CIGSe) layer structure. The CdS/CIGSe interface is the central component in next-generation chalcopyrite thin-film photovoltaic devices. By analyzing both, the (unscattered) core-level peaks and the inelastic background, and by varying the excitation photon energy from 2.1 up to 14 keV, we can derive photoemission information over a broad range of electron kinetic energies and, hence, sampling depths. With this complementary information, the CdS film thickness of a CdS/CIGSe interface can be accurately determined as a function of the CdS deposition time. …
Evaluating Deep-Learning Models For Debris-Covered Glacier Mapping,
2021
University of Dayton
Evaluating Deep-Learning Models For Debris-Covered Glacier Mapping, Zhiyuan Xie, Vijayan K. Asari, Umesh K. Haritashya
Electrical and Computer Engineering Faculty Publications
In recent decades, mountain glaciers have experienced the impact of climate change in the form of accelerated glacier retreat and other glacier-related hazards such as mass wasting and glacier lake outburst floods. Since there are wide-ranging societal consequences of glacier retreat and hazards, monitoring these glaciers as accurately and repeatedly as possible is important. However, the accurate glacier boundary, especially the debriscovered glacier (DCG) boundary, which is one of the primary inputs in many glacier analyses, remains a challenge even after many years of research using conventional remote sensing methods or machine-learning methods. The GlacierNet, a deep-learning-based approach, utilized the …
Study Of Thick Indium Gallium Nitride Graded Structures For Future Solar Cell Applications,
2021
University of Arkansas, Fayetteville
Study Of Thick Indium Gallium Nitride Graded Structures For Future Solar Cell Applications, Manal Abdullah Aldawsari
Graduate Theses and Dissertations
Indium gallium nitride (InxGa1-xN) materials have held great potential for the optoelectronic industry due to their electrical and optical properties. The tunable band gap that can span the solar spectrum was one of the most significant features that attracted researchers’ attention. The band gap can be varied continuously from 0.77 eV for InN to 3.42 eV for GaN, covering the solar spectrum from near infrared to near ultraviolet. Additionally, it has a high absorption coefficient on the order of ∼105 cm−1, a direct band gap, high radiation resistance, thermal stability, and so on. Nevertheless, the epitaxial growth of high quality …
Investigation Of Optical And Structural Properties Of Gesn Heterostructures,
2021
University of Arkansas, Fayetteville
Investigation Of Optical And Structural Properties Of Gesn Heterostructures, Oluwatobi Gabriel Olorunsola
Graduate Theses and Dissertations
Silicon (Si)-based optoelectronics have gained traction due to its primed versatility at developing light-based technologies. Si, however, features indirect bandgap characteristics and suffers relegated optical properties compared to its III-V counterparts. III-Vs have also been hybridized to Si platforms but the resulting technologies are expensive and incompatible with standard complementary-metal-oxide-semiconductor processes. Germanium (Ge), on the other hand, have been engineered to behave like direct bandgap material through tensile strain interventions but are well short of attaining extensive wavelength coverage. To create a competitive material that evades these challenges, transitional amounts of Sn can be incorporated into Ge matrix to form …
Incorporation Of Zinc In Pre-Alloyed Cuin[Zn]S2/Zns Quantum Dots,
2021
University of Arkansas, Fayetteville
Incorporation Of Zinc In Pre-Alloyed Cuin[Zn]S2/Zns Quantum Dots, Jean Carlos Morales Orocu
Graduate Theses and Dissertations
Since the early 2000s heavy-metal-free quantum dots (QDs) such as CuInS2/ZnS have attempted to replace CdSe, their heavy-metal-containing counterparts. CuInS2/ZnS is synthesized in a two-step process that involves the fabrication of CuInS2 (CIS) nanocrystals (NCs) followed by the addition of zinc precursors. Instead of the usual core/shell architecture often exhibited by binary QDs, coating CIS QDs results in alloyed and/or partially alloyed cation-exchange (CATEX) QDs. The effect that zinc has on the properties of CIS NCs was studied by incorporating zinc during the first step of the synthesis. Different In:Cu:Zn ratios were employed in this study, maintaining a constant 4:1 …
Sigesn Light-Emitting Devices: From Optical To Electrical Injection,
2021
University of Arkansas, Fayetteville
Sigesn Light-Emitting Devices: From Optical To Electrical Injection, Yiyin Zhou
Graduate Theses and Dissertations
Si photonics is a fast-developing technology that impacts many applications such as data centers, 5G, Lidar, and biological/chemical sensing. One of the merits of Si photonics is to integrate electronic and photonic components on a single chip to form a complex functional system that features compact, low-cost, high-performance, and reliability. Among all building blocks, the monolithic integration of lasers on Si encountered substantial challenges. Si and Ge, conventional epitaxial material on Si, are incompetent for light emission due to the indirect bandgap. The current solution compromises the hybrid integration of III-V lasers, which requires growing on separate smaller size substrates …
Growth Of Pseudomorphic Gesn At Low Pressure With Sn Composition Of 16.7%,
2021
University of Arkansas, Fayetteville
Growth Of Pseudomorphic Gesn At Low Pressure With Sn Composition Of 16.7%, Joshua Grant, Grey Abernathy, Oluwatobi Olorunsola, Solomon Opeyemi Ojo, Sylvester Amoah, Emmanuel Wangila, Samir K. Saha, Abbas Sabbar, Wei Du, Murtadha Alher, Bao-Hua Li, Shui-Qing Yu
Physics Faculty Publications and Presentations
Group-IV alloy GeSn holds great promise for the high-performance optoelectronic devices that can be monolithically integrated on Si for near- and mid-infrared applications. Growth of GeSn using chemical vapor deposition technique with various Sn and Ge precursors has been investigated worldwide. To achieve relatively high Sn incorporation, the use of higher pressure and/or higher order Ge hydrides precursors were reported. In this work, we successfully demonstrated the growth of high-quality GeSn with Sn composition of 16.7% at low pressure of 12 Torr. The alloy was grown using the commercially available GeH4 and SnCl4 precursors via a chemical vapor …
Polarization-Resolved Extreme-Ultraviolet Second-Harmonic Generation From Linbo3,
2021
Berkeley College of Chemistry
Polarization-Resolved Extreme-Ultraviolet Second-Harmonic Generation From Linbo3, Can B. Uzundal, Sasawat Jamnuch, Emma Berger, Clarisse Woodahl, Paul Manset, Yasuyuki Hirata, Toshihide Sumi, Angelique Amado, Hisazumi Akai, Yuya Kubota, Shigeki Owada, Kensuke Tono, Makina Yabashi, John W. Freeland, Craig P. Schwartz, Walter S. Drisdell
Nevada Extreme Conditions Laboratory Faculty Research
Second harmonic generation (SHG) spectroscopy ubiquitously enables the investigation of surface chemistry, interfacial chemistry, as well as symmetry properties in solids. Polarization-resolved SHG spectroscopy in the visible to infrared regime is regularly used to investigate electronic and magnetic order through their angular anisotropies within the crystal structure. However, the increasing complexity of novel materials and emerging phenomena hampers the interpretation of experiments solely based on the investigation of hybridized valence states. Here, polarization-resolved SHG in the extreme ultraviolet (XUV-SHG) is demonstrated for the first time, enabling element-resolved angular anisotropy investigations. In noncentrosymmetric LiNbO3, elemental contributions by lithium and niobium are …
Single-Molecule Localization Microscopy Of 3d Orientation And Anisotropic Wobble Using A Polarized Vortex Point Spread Function,
2021
Washington University in St. Louis
Single-Molecule Localization Microscopy Of 3d Orientation And Anisotropic Wobble Using A Polarized Vortex Point Spread Function, Tianben Ding, Matthew D. Lew
Electrical & Systems Engineering Publications and Presentations
Within condensed matter, single fluorophores are sensitive probes of their chemical environments, but it is difficult to use their limited photon budget to image precisely their positions, 3D orientations, and rotational diffusion simultaneously. We demonstrate the polarized vortex point spread function (PSF) for measuring these parameters, including characterizing the anisotropy of a molecule’s wobble, simultaneously from a single image. Even when imaging dim emitters (∼500 photons detected), the polarized vortex PSF can obtain 12 nm localization precision, 4°–8° orientation precision, and 26° wobble precision. We use the vortex PSF to measure the emission anisotropy of fluorescent beads, the wobble dynamics …
Resampling And Super-Resolution Of Hexagonally Sampled Images Using Deep Learning,
2021
University of Dayton
Resampling And Super-Resolution Of Hexagonally Sampled Images Using Deep Learning, Dylan Flaute, Russell C. Hardie, Hamed Elwarfalli
Electrical and Computer Engineering Faculty Publications
Super-resolution (SR) aims to increase the resolution of imagery. Applications include security, medical imaging, and object recognition. We propose a deep learning-based SR system that takes a hexagonally sampled low-resolution image as an input and generates a rectangularly sampled SR image as an output. For training and testing, we use a realistic observation model that includes optical degradation from diffraction and sensor degradation from detector integration. Our SR approach first uses non-uniform interpolation to partially upsample the observed hexagonal imagery and convert it to a rectangular grid. We then leverage a state-of-the-art convolutional neural network (CNN) architecture designed for SR …
Recent Advances In Silver Nanoparticle-Based Electrochemical Sensors For Determining Organic Pollutants In Water,
2021
Menoufia University
Recent Advances In Silver Nanoparticle-Based Electrochemical Sensors For Determining Organic Pollutants In Water, Ziad Khalifa, Moustafa Zahran, Magdy Zahran, Magdi Abdelazzem
Chemical Engineering
Water pollutants have attracted great attention because of their negative effect on human health. Accordingly, various analytical techniques have been investigated to detect water pollutants as a preliminary step for their control. This review highlights silver nanoparticles (AgNPs) as promising electrochemical probes studied for detecting organic pollutants. Electrochemical sensors can be fabricated by modifying electrode surfaces using AgNPs via different techniques, such as electrochemical deposition, drop casting, spin coating, sticking, and transfer sticking, as well as carbon paste-based modification. AgNPs at electrode surfaces can be identified by their stripping to form Ag+ with a particular oxidation peak. Additionally, they can …
A Unified Framework Of Deep Learning-Based Facial Expression Recognition System For Diversified Applications,
2021
Aliah University
A Unified Framework Of Deep Learning-Based Facial Expression Recognition System For Diversified Applications, Sanoar Hossain, Saiyed Umer, Vijayan K. Asari, Ranjeet Kumar Rout
Electrical and Computer Engineering Faculty Publications
This work proposes a facial expression recognition system for a diversified field of appli- cations. The purpose of the proposed system is to predict the type of expressions in a human face region. The implementation of the proposed method is fragmented into three components. In the first component, from the given input image, a tree-structured part model has been applied that predicts some landmark points on the input image to detect facial regions. The detected face region was normalized to its fixed size and then down-sampled to its varying sizes such that the advantages, due to the effect of multi-resolution …
Characterization Of Anisotropic Materials Using Scattered Field Measurements,
2021
Air Force Institute of Technology
Characterization Of Anisotropic Materials Using Scattered Field Measurements, Hirsch M. Chizever
Theses and Dissertations
This research uses monostatic far-zone scattered field measurements to estimate the permittivity of biaxial materials at X-Band. Utilizing Radar Cross Section (RCS) measurement techniques, this effort examines the efficacy of whole-sample TEM illumination in the estimation of anisotropic permittivity, in contrast with traditional subsample illumination methods. The research examines the impact that dielectric supports have on measurement error and uncertainty in permittivity estimates. Following an incremental approach, the research first demonstrates successful estimation of permittivity for isotropic spheres followed by a Teflon isotropic cube. Finally, the method is applied to uniaxial and biaxial cubes whose anisotropic permittivity is validated through …
A Compact 1200 V, 700 A, Igbt-Based Pulse Generator For Repetitive Transcranial Magnetic Stimulation In Vivo Laboratory Experiments On Small Animals,
2021
University of Nevada, Las Vegas
A Compact 1200 V, 700 A, Igbt-Based Pulse Generator For Repetitive Transcranial Magnetic Stimulation In Vivo Laboratory Experiments On Small Animals, Daniel Senda, Haley Strong, Dustin Hines, Rochelle Hines, R. Jacob Baker
Psychology Faculty Research
An insulated-gate bipolar transistor (IGBT) pulse generator for repetitive transcranial magnetic stimulation used for in vivo laboratory experiments on small animals, such as mice, is reported. The pulse generator is based upon an IGBT that can switch 700 A of current for 1 ms and that has a DC breakdown voltage of 1200 V. The duration of the design’s output pulse is controlled by, and follows, an input trigger pulse. The voltage amplitude of the output pulses is determined by an external high-voltage power supply and the energy stored in a 330 µF capacitor bank. The approach enables the amplitude …
The Effect Of A Ferrite-Core Relay Vs. An Air-Core Relay On The Output Power Characteristics Of A Three-Coil Wireless Power Transfer System,
2021
Portland State University
The Effect Of A Ferrite-Core Relay Vs. An Air-Core Relay On The Output Power Characteristics Of A Three-Coil Wireless Power Transfer System, Jakob L. White
University Honors Theses
The purpose of this thesis is to determine the effect of using a ferrite-core relay on the output power characteristics of a three-coil, parallel-tuned, domino-resonator wireless power transfer (WPT) system in comparison to the effect of using an air-core relay in such a system. First, a general mathematical model is presented to describe both the ferrite-core-relay system and the air-core-relay system and to calculate their output power characteristics for seven different resistive loads at each of five different distance configurations between the coils. Next, experimental results are analyzed and compared to the mathematical results to confirm model accuracy. Finally, the …
Wavelength And Power Dependence On Multilevel Behavior Of Phase Change Materials,
2021
University of Dayton
Wavelength And Power Dependence On Multilevel Behavior Of Phase Change Materials, Gary A. Sevison, Joshua A. Burrow, Haiyun Guo, Andrew M. Sarangan, Joshua R. Hendrickson, Imad Agha
Electro-Optics and Photonics Faculty Publications
We experimentally probe the multilevel response of GeTe, Ge2Sb2Te5 (GST), and 4% tungsten-doped GST (W-GST) phase change materials (PCMs) using two wavelengths of light: 1550 nm, which is useful for telecom-applications, and near-infrared 780 nm, which is a standard wavelength for many experiments in atomic and molecular physics. We find that the materials behave differently with the excitation at the different wavelengths and identify useful applications for each material and wavelength. We discuss thickness variation in the thin films used as well and comment on the interaction of the interface between the material and the substrate with regard to the …
Study And Design Of Array And Beamsteering Antennas For Millimeter Wave Band Application,
2021
Boise State University
Study And Design Of Array And Beamsteering Antennas For Millimeter Wave Band Application, Saeideh Shad
Boise State University Theses and Dissertations
Millimeter wave (mmWave) communication systems have attracted significant interest regarding supporting high data rate of Gigabit/s communications for the new generation of wireless communication networks. MmWave communication systems have frequency ranges in between 30 and 300 GHz wherein an enormous amount of unused bandwidth is available. Although the available bandwidth of mmWave frequencies is promising for high data rate communications, the propagation characteristics of mmWave frequencies are significantly different from microwave frequency band in terms of path loss, diffraction and blockage, and atmospheric absorption. In general, the overall losses of mmWave signals are significantly larger than that of microwave signals …
Experimental Observation Of Topological Z2 Excitonpolaritons In Transition Metal Dichalcogenide Monolayers,
2021
CUNY City College
Experimental Observation Of Topological Z2 Excitonpolaritons In Transition Metal Dichalcogenide Monolayers, Mengyao Li, Ivan Sinev, Fedor Benimetskiy, Tatyana Ivanova, Ekaterina Khestanova, Svetlana Kiriushechkina, Anton Vakulenko, Sriram Guddala, Maurice Skolnick, Vinod M. Menon, Dmitry Krizhanovskii, Andrea Alù, Anton Samusev, Alexander B. Khanikaev
Publications and Research
The rise of quantum science and technologies motivates photonics research to seek new platforms with strong light-matter interactions to facilitate quantum behaviors at moderate light intensities. Topological polaritons (TPs) offer an ideal platform in this context, with unique properties stemming from resilient topological states of light strongly coupled with matter. Here we explore polaritonic metasurfaces based on 2D transition metal dichalcogenides (TMDs) as a promising platform for topological polaritonics. We show that the strong coupling between topological photonic modes of the metasurface and excitons in TMDs yields a topological polaritonic Z2 phase. We experimentally confirm the emergence of one-way …
Optical Switching Performance Of Thermally Oxidized Vanadium Dioxide With An Integrated Thin Film Heater,
2021
University of Dayton
Optical Switching Performance Of Thermally Oxidized Vanadium Dioxide With An Integrated Thin Film Heater, Andrew M. Sarangan, Gamini Ariyawansa, Ilya Vitebskiy, Igor Anisimov
Electro-Optics and Photonics Faculty Publications
Optical switching performance of vanadium dioxide produced by thermal oxidation of vanadium is presented in this paper. A 100nm thick vanadium was oxidized under controlled conditions in a quartz tube furnace to produce approximately 200nm thick VO2. The substrate was appropriately coated on the front and back side to reduce reflection in the cold state, and an integrated thin film heater was fabricated to allow in-situ thermal cycling. Electrical measurements show a greater than three orders of magnitude change in resistivity during the phase transition. Optical measurements exhibit 70% transparency at 1500nm and about 15dB extinction across a wide spectral …
Computational Modeling Of Black Phosphorus Terahertz Photoconductive Antennas Using Comsol Multiphysics With Experimental Comparison Against A Commercial Lt-Gaas Emitter,
2021
University of Arkansas, Fayetteville
Computational Modeling Of Black Phosphorus Terahertz Photoconductive Antennas Using Comsol Multiphysics With Experimental Comparison Against A Commercial Lt-Gaas Emitter, Jose Isaac Santos Batista
Graduate Theses and Dissertations
This thesis presents computational models of terahertz (THz) photoconductive antenna (PCA) emitter using COMSOL Multiphysics commercial package. A comparison of the computer simulated radiated THz signal against that of an experimentally measured signal of commercial reference LT-GaAs emitter is presented. The two-dimensional model (2D) aimed at calculating the photoconductivity of a black phosphorus (BP) PCA at two laser wavelengths of 780 nm and 1560 nm. The 2D model was applied to the BP PCA emitter and the LT-GaAs devices to compare their simulated performance in terms of the photocurrent and radiated THz signal pulse. The results showed better performance of …
