Physics Commons^™

Quantitative, Photocurrent Multidimensional Coherent Spectroscopy, Adam Halaoui

Electronic Theses and Dissertations

Multidimensional coherent spectroscopy (MDCS) is a quickly growing field that has a lot of advantages over more conventional forms of spectroscopy. These advantages all come from the fact that MDCS allows us to get time resolved correlated emission and absorption spectra using very precisely chosen interactions between the density matrix and the excitation laser. MDCS spectra gives the researcher a lot of information that can be extracted purely through qualitative analysis. This is possible because state couplings are entirely separated on the spectra, and once we know how to read the data, we can see how carriers transport in the …

Fabrication Of Black Phosphorus Terahertz Photoconductive Antennas, Nathan Tanner Sawyers

Physics Undergraduate Honors Theses

Terahertz (THz) photoconductive antennas (PCAs) using 40nm thin-film flakes of black phosphorus (BP) and hexagonal boron nitride (hBN) have been shown computationally to be capable of THz emission comparable to those based on GaAs [2]. In this paper, I briefly describe the scientific and practical interest in THz emissions and explain what warrants research into black phosphorus as a photoconductive semiconductor in THz devices. Furthermore, I outline the basic principle of how these antennas work and mention alternative designs produced by other researchers in the past. Finally, I summarize the fabrication process of these antennas, as well as the measurements …

Gate-Controlled Quantum Dots In Two-Dimensional Tungsten Diselenide And One-Dimensional Tellurium Nanowires, Shiva Davari Dolatabadi

Graduate Theses and Dissertations

This work focuses on the investigation of gate-defined quantum dots in two-dimensional transition metal dichalcogenide tungsten diselenide (WSe2) as a means to unravel mesoscopic physical phenomena such as valley-contrasting physics in WSe2 flakes and its potential application as qubit, as well as realizing gate-controlled quantum dots based on elementaltellurium nanostructures which may unlock the topological nature of the host material carriers such as Weyl states in tellurium nanowires.The fabrication and characterization of gate-defined hole quantum dots in monolayer and bilayer WSe2 are reported. The gate electrodes in the device design are located above and below the WSe2 nanoflakes to accumulate …

Engineering Rare-Earth Based Color Centers In Wide Bandgap Semiconductors For Quantum And Nanoscale Applications, Gabriel I. López-Morales

Dissertations, Theses, and Capstone Projects

For many years, atomic point-defects have been readily used to tune the bulk properties of solid-state crystalline materials, for instance, through the inclusion of elemental impurities (doping) during growth, or post-processing treatments such as ion bombardment or high-energy irradiation. Such atomic point-defects introduce local ‘incompatible’ chemical interactions with the periodic atomic arrangement that makes up the crystal, resulting for example in localized electronic states due to dangling bonds or excess of electrons. When present in sufficient concentrations, the defects interact collectively to alter the overall bulk properties of the host material. In the low concentration limit, however, point-defects can serve …

Electrical And Optical Characterization Of Two-Dimensional Semiconductors Using Ultrafast Spectroscopy, Pan Adhikari

All Dissertations

The emergence of two-dimensional (2D) layered materials provides unprecedented opportunities for studying excitonic physics due to the strong Coulomb interaction between the electron-hole pair. Because of the reduced dimensionality and weak dielectric screening, the exciton is stable at room temperature, unlike bulk semiconductors. The evolution from low to high carrier density for optical gain in 2D semiconductors involves insulating exciton gas, exciton condensation, co-existence of various excitonic complexes, electron-hole plasmas (EHPs), or electron-hole liquids (EHLs), leading to the Mott transition. Strong interaction among the excitons, such as exciton-exciton annihilation (EEA), serves as a hot-carrier generation. A bound exciton dissociates into …

Impact Of Proton And Neutron Irradiation On Carrier Transport Properties In Ga2o3, Andrew C. Silverman

Honors Undergraduate Theses

This project studies the properties of minority charge carriers in beta gallium oxide (β -Ga₂O₃). The behavior of minority carriers is of high importance as it greatly affects conduction and consequently device performance. Cathodoluminescence (CL) spectroscopy and EBIC (Electron Beam Induced Current) are the main experimental techniques used to study minority carrier behavior.

High energy radiation affects minority carrier properties through damage to the material and through the production of carrier traps that reduce the conductivity and mobility of the material. In this investigation, we study the effects of various kinds of high energy radiation on …

Theoretical Investigations Of The Structural, Dynamical, Electronic, Magnetic, And Thermoelectric Properties Of Corhysi (Y = Cr, Mn) Quaternary Heusler Alloys, Abdullah Hussain Hzzazi

Graduate Theses and Dissertations

Thermoelectric materials have potential properties for utilizing waste heat. The computations are used to estimate the electronic structure of CoRhYSi (Y = Cr, Mn) Quaternary Heusler alloys, as well as their elastic and magnetic characteristics. The full-potential linearized augmented plane wave is used in the calculations. The exchange-correlations are addressed using Perdew–Burke and Ernzerhof's generalized gradient approximation (GGA-PBE). With the exception of CoRhCrSi and CoRhMnSi, which are simple ferromagnets that are approximately half metallic in nature, electronic structure calculations demonstrate that these compounds have a gap in the minority states band and are obviously half-metallic ferromagnets. The magnetic moments of …

Design And Characterization Of Standard Cell Library Using Finfets, Phanindra Datta Sadhu

Master's Theses

The processors and digital circuits designed today contain billions of transistors on a small piece of silicon. As devices are becoming smaller, slimmer, faster, and more efficient, the transistors also have to keep up with the demands and needs of the daily user. Unfortunately, the CMOS technology has reached its limit and cannot be used to scale down due to the transistor's breakdown caused by short channel effects. An alternative solution to this is the FinFET transistor technology, where the gate of the transistor is a three dimensional fin that surrounds the transistor and prevents the breakdown caused by scaling …

Ga-Based Iii-V Semiconductor Photoanodes For Solar Fuels And Novel Techniques To Investigate Their Photocorrosion., Sahar Pishgar

Electronic Theses and Dissertations

Solar energy is one of the most abundant renewable energy sources. However, the diurnal variation of the sun as well as seasonal and weather effects, limits the widespread global implementation of solar energy. Thus, Cost-effective energy storage is critical to overcome the intermittent nature of solar energy available on the earth. Photoelectrolysis of water to oxygen and hydrogen fuel is a promising large-scale solution to store intermittent solar energy in a dense and portable form. Photoelectrochemical (PEC) water-splitting, or artificial photosynthesis, research strives to develop a semiconductor photoelectrode with both high efficiency and long-term stability. Semiconductors of the III–V class …

Fundamental Transport Properties In Silicon Quantum Structures, Nazban M. Darukhanawalla

Electronic Thesis and Dissertation Repository

In the field of silicon photonics, there is an effort to bridge the gap between electrical and optical signals on a single platform, creating a need for Si-based light sources. In this project, Si quantum structures – Si quantum wells and quantum dots in SiO2 were fabricated via solid state precipitation methods. Their properties were studied using X-ray photoelectron spectroscopy, photoluminescence and I-V measurements. Rutherford backscattering spectroscopy was used for depth analysis in monitoring the Si distribution. Different electrical transport mechanisms were explored to understand how an ensemble of silicon QD’s or a silicon quantum well behaves in an SiO2 …

Wavelength Swept Photonic Crystal Laser, Sharon Marie Butler

Theses

Photonics has become integral to society, based on its ability to sense the environment, to manipulate materials and to transport information. The dominance of silicon electronics has made silicon photonics a compelling vision, but difficulties with light emission have caused delays in implementation and an enduring role for III-V materials. The research conducted in this Ph.D. thesis involves study and utilisation of a combination of the optical gain of Indium Phosphide with the precision and energy of silicon nanophotonics in a novel family of lasers. A continuously tunable akinetic reflective filter is exploited to obtain a wavelength swept laser. The …

Data Processing & Analysis For Atomic Force Microscopy (Afm), Molly Mcdonough, Polievkt Perov, Walter Johnson, Stevan Radojev

Undergraduate Theses and Capstone Projects

Scanning Probe Microscopy (SPM) has become a critical tool for characterization of materials in fields such as physics, material science, chemistry, and biology. Atomic Force Microscopy (AFM) is an increasingly useful technique because of its high resolution in three dimensions, the sample does not need to be conductive, and the technique does not need to take place in vacuum. AFM can image a wide variety of topographies and many different types of materials. AFM can deliver 3D topography information from the angstrom level to the micron scale with high resolution. One of the most important aspects of Atomic Force Microscopy …

Modeling Adsorption Of Molecular Semiconductors On An Ionic Substrate: Ptcda And Cupc On Nacl, Julia Thorpe

Scholars Week

Molecular adsorption can be accurately studied using computational chemistry methods. Experimental results suggest that molecular geometry and energies can be influenced by the presence of thin film substrates as well as surrounding molecules. In our study, Density Functional Theory (DFT) and Molecular Mechanics (MM) are used to model the configurations of the organic semiconducting materials, Perylene Tetracarboxylic Dianhydride, C24H8O6 (PTCDA), and Copper Phthalocyanine, C34H16CuN8 (CuPc), as adsorbed on single and double layer NaCl substrates of various dimensions and charge settings. After geometry and charge optimization of the molecules using DFT, the molecular geometries are optimized under different environments using computational …

Ii-Vi Type-Ii Quantum Dot Superlattices For Novel Applications, Vasilios Deligiannakis

Dissertations, Theses, and Capstone Projects

In this thesis, we discuss the growth procedure and the characterization results obtained for epitaxially grown submonolayer type-II quantum dot superlattices made of II-VI semiconductors. We have investigated the spin dynamics of ZnSe layers with embedded type-II ZnTe quantum dots and the use of (Zn)CdTe/ZnCdSe QDs for intermediate band solar cell (IBSC). Samples with a higher quantum dot density exhibit longer electron spin lifetimes, up to ~1 ns at low temperatures. Tellurium isoelectronic centers, which form in the ZnSe spacer regions as a result of the growth conditions, were also probed. A new growth sequence for type-II (Zn)CdTe/ZnCdSe (QDs) was …

Hybrid Frequency Modulated Silicon Photonic Crystal Laser, Andrei Bakoz

Theses

Silicon photonics takes advantage of the mature complementary metal-oxide semiconductor (CMOS) infrastructure and processes, and is actively pursued for the implementation of complex optical components and photonic integrated circuits (PICs) at low cost and high volumes. Despite a constant refinement of silicon photonics technology to meet the evolving requirements for applications, the poor light emission ability of silicon remains a constraint. As a result, the most essential building block of an optical system, an efficient light emitter, remains absent in PICs based on silicon. This thesis is focused on study of the potential of an external cavity (EC) hybrid III-V …

Anomalous Stranski-Krastanov Growth Of (111)-Oriented Quantum Dots With Tunable Wetting Layer Thickness, Christopher F. Schuck, Simon K. Roy, Trent Garrett, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In_0.52Al_0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers’ attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we demonstrate that for GaAs(111)A QDs, we …

Using Fundamental Properties Of Light To Investigate Photonic Effects In Condensed Matter And Biological Tissues, Laura A. Sordillo

Dissertations and Theses

Light possesses characteristics such as polarization, wavelength and coherence. The interaction of light and matter, whether in a semiconductor or in a biological sample, can reveal important information about the internal properties of a system. My thesis focuses on two areas: photocarriers in gallium arsenide and biomedical optics. Varying the excitation wavelength can be used to study both biological tissue and condensed matter. I altered the excitation wavelengths to be in the longer near-infrared (NIR) optical windows, in the shortwave infrared (SWIR) range, a wavelength region previously thought to be unusable for medical imaging. With this method, I acquired high …

Elaboration And Study Of Structural And Optical Properties Of Aubr Nanocrystalsdispersed In Kbr Single Crystals, Hanane Zaioune, Fouzia Zehani, Noureddine Boutaoui, Badis Khennaoui

Turkish Journal of Physics

The structural and optical properties of the AuBr nanocrystals embedded in the KBr single crystals grown by the Czochralski method were studied using several techniques. The X-ray diffraction reveals their formation and incorporation. The crystallite average radii calculated from XRD using the Scherrer's formula was found to vary between 19 and 39 nm. The photoluminescence spectra obtained on these same samples present an emission band located at 1.91 eV (650 nm), which can be attributed to the orange luminescence of AuBr nanocrystals. However, the photoluminescence excitation measurements of these nanocrystals exhibit an excitation band located at 3.44 eV (360 nm), …

Exploring Gated Nanoelectronic Devices Fabricated From 1d And 2d Materials, Prathamesh A. Dhakras

Legacy Theses & Dissertations (2009 - 2024)

One and two dimensional materials are being extensively researched toward potential application as ultra-thin body channel materials. The difficulty of implementing physical doping methods in these materials has necessitated various alternative doping schemes, the most promising of which is the electrostatic gating technique due to its reconfigurability. This dissertation explores the different fundamental devices that can be fabricated and characterized by taking advantage of the electrostatic gating of individual single-walled carbon nanotubes (SWNTs), dense SWNT networks and exfoliated 2D tungsten diselenide (WSe2) flakes.

Electron Transport In One And Two Dimensional Materials, Samuel William Lagasse

Legacy Theses & Dissertations (2009 - 2024)

This dissertation presents theoretical and experimental studies in carbon nanotubes (CNTs), graphene, and van der Waals heterostructures. The first half of the dissertation focuses on cutting edge tight-binding-based quantum transport models which are used to study proton irradiation-induced single-event effects in carbon nanotubes [1], total ionizing dose effects in graphene [2], quantum hall effect in graded graphene p-n junctions [3], and ballistic electron focusing in graphene p-n junctions [4]. In each study, tight-binding models are developed, with heavy emphasis on tying to experimental data. Once benchmarked against experiment, properties of each system which are difficult to access in the laboratory, …

Nonlinear Coupled Effects In Nanomaterials, Sia Bhowmick

Theses and Dissertations (Comprehensive)

Materials at the nanoscale have different chemical, structural, and optoelectrical properties compared to their bulk counterparts. As a result, such materials, called nanomaterials, exhibit observable differences in certain physical phenomena. One such resulting phenomenon called the piezoelectric effect has played a crucial role in miniature self-powering electronic devices called nanogenerators which are fabricated by using nanostructures, such as nanowires, nanorods, and nanofilms. These devices are capable of harvesting electrical energy by inducing mechanical strain on the individual nanostructures. Electrical energy created in this manner does not have environmental limitations. In this thesis, important coupled effects, such as the nonlinear piezoelectric …

Generalizable Modeling Of Charge Transport In Single Electron Transistor Devices: Application To Thermal Sensitivity In Semiconducting Island Systems, Paniz Khanmohammadi Hazaveh

Dissertations, Master's Theses and Master's Reports

Electronic devices, especially MOSFETs, have been dimensionally scaled down to enhance operation of integrated circuits, addressing challenges such as current leakage, fluctuation of intrinsic semiconductor properties, and power dissipation. Reaching dimensions below 20 nm, there are fundamental limitations that are difficult to overcome, driving alternative device paradigms to be sought utilizing the quantum mechanical behavior of electrons. Single electron transistor (SET) devices are examples of a new generation of low-power transistors designed to transport information via single electron tunneling through one or more islands separated by tunnel junctions. Experimentally explored SET devices have shown that there are advantages to using …

Synergistic Interactions Of H2 And N2 With Molten Gallium In The Presence Of Plasma, Maria L. Carreon, Daniel F. Jaramillo-Cabanzo, Indira Chaudhuri, Madhu Menon, Mahendra K. Sunkara

Physics and Astronomy Faculty Publications

The present study examines the interaction of hydrogen and nitrogen plasmas with gallium in an effort to gain insights into the mechanisms behind the synergetic effect of plasma and a catalytic metal. Absorption/desorption experiments were performed, accompanied by theoretical-computational calculations. Experiments were carried out in a plasma-enhanced, Ga-packed, batch reactor and entailed monitoring the change in pressure at different temperatures. The results indicated a rapid adsorption/dissolution of the gas into the molten metal when gallium was exposed to plasma, even at a low temperature of 100 °C. The experimental observations, when hydrogen was used, indicate that gallium acts as a …

Detecting Majorana Fermion Induced Crossed Andreev Reflection, Lei Fang

Dissertations, Theses, and Capstone Projects

This dissertation is devoted to a study of detecting the Majorana fermion induced crossed Andreev reflection.

Majorana fermions are particles that constitute their own antiparticles. In condensed matter physics, Majorana fermions are zero energy modes that reside at edges or around vortices of topological superconductors. The special properties of Majorana fermions result in their potential to conduct topological quantum computation, which has been attracting a lot of current research. One of the most important issues in the field of the Majorana fermion physics now is to detect their existence in realistic systems. Among many classes of detecting methods, a transport …

Synthesis And Fundamental Property Studies Of Energy Material Under High Pressure., Meysam Akhtar

Electronic Theses and Dissertations

Recently, high-pressure science and technology has flourished and rapidly advanced to impact a wide domain of materials and physical sciences. One of the most substantial technological developments is the integration of samples at ultrahigh pressure with a wide range of in-situ probing techniques. Applications of extreme pressure have significantly enriched our understanding of the electronic, phonon, and doping effects on the newly emerged two-dimensional (2D) materials. Under high pressure, materials’ atomic volume radically decreases, and electronic density rises, which will lead to extraordinary chemical reaction kinetic and mechanisms. The promising capability of high pressure combine with the significance of novel …

Quantum Dot Band Gap Investigations, John Ryan Peterson

Student Works

Improving solar panel efficiency has become increasingly important as the world searches for cheap renewable energy. Recent developments in the industry have focused on multi-layer cells, some of which use semiconducting dyes to absorb light in place of crystalline solids. In this paper, I characterize various dyes recently synthesized for use in solar panels. These dyes contain semiconducting nanoparticles enclosed primarily by the protein ferritin to limit particle size. The band gaps were measured using either optical absorption spectroscopy or measuring the photoluminescence spectrum, depending on the type of semiconductor. The results indicate that both manganese oxide and lead sulfide …

Evaluation Of Hydrothermally Synthesized Uranium Dioxide For Novel Semiconductor Applications, Christopher M. Young

Theses and Dissertations

Neutron radiation detection is an important part of the national strategy for nonproliferation efforts worldwide. Key to the success of these programs is detector material development which establishes the limits of efficiency, sensitivity, and power usage for a detector of practical use. This research focused upon the study of neutron detection using single crystal actinide compounds, specifically UO2, taking advantage of the successful hydrothermal synthesis of UO2 at the Air Force Research Laboratories. Initial indications are that this material may be of sufficient quality for semiconductor application.

Nanostructured Organic/Inorganic Semicondutor Photovoltaics: Investigation On Morphology And Optoelectronics Performance, Aruna Wanninayake

Theses and Dissertations

Organic solar cell is a promising technology because of the versatility of organic materials in terms of tunability of their electrical and optical properties. In addition, their relative insensitivity to film imperfections potentially allows for very low-cost high-throughput roll-to-roll processing. However, the power conversion efficiency of organic solar cell is still limited and needs to be improved in order to be competitive with grid parity. This work is focused on the design and characterization of a new organic/inorganic hybrid device to enhance the efficiency factors of bilayer organic solar cells such as: light absorption, exciton diffusion, exciton dissociation, charge transportation …

Zncdmgse As A Materials Platform For Advanced Photonic Devices: Broadband Quantum Cascade Detectors And Green Semiconductor Disk Lasers, Joel De Jesus

Dissertations, Theses, and Capstone Projects

The ZnCdMgSe family of II-VI materials has unique and promising characteristics that may be useful in practical applications. For example they can be grown lattice matched to InP substrates with lattice matched bandgaps that span from 2.1 to 3.5 eV, they can be successfully doped n-type, have a large conduction band offset (CBO) with no intervalley scattering present when strained, they have lower average phonon energies, and the InP lattice constant lies in the middle of the ZnSe and CdSe binaries compounds giving room to experiment with tensile and compressive stress. However they have not been studied in detail for …

Properties Of Amorphous Transparent Conducting And Semiconducting Oxides From First Principles, Rabi Khanal

Doctoral Dissertations

"Amorphous transparent conducting and semiconducting oxides possess properties superior or comparable to their crystalline counterparts. The structure-property relationship in amorphous oxides is not nearly as well understood as in the case of the crystalline transparent conducting oxides. We have employedab initio molecular dynamics and a liquid quench approach to simulate amorphous oxide structures and performed density functional-based calculations to study the electronic properties of several amorphous conducting and semiconducting oxides with various cation compositions.

The effect of amorphization in oxides was investigated by taking indium oxide as a progenitor of the system. From the thorough study it was confirmed …