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Articles 1 - 30 of 34
Full-Text Articles in Physics
Encapsulated 2d Materials And The Potential For 1d Electrical Contacts, Sarah Wittenburg
Encapsulated 2d Materials And The Potential For 1d Electrical Contacts, Sarah Wittenburg
Physics Undergraduate Honors Theses
The utilization of two-dimensional materials and heterostructures, particularly graphene and hexagonal boron nitride, have garnered significant attention in the realm of nanoelectronics due to their unique properties and versatile functionalities. This study focuses on the synthesis and fabrication processes of monolayer graphene encapsulated between layers of hBN, aiming to explore the potential of these heterostructures for various electronic applications. The encapsulation of graphene within hBN layers not only enhances device performance but also shields graphene from environmental contaminants, ensuring long-term stability. Experimental techniques, including mechanical exfoliation and stamp-assisted transfer, are employed to construct three-layer stacks comprising hBN-graphene-hBN. The fabrication process …
The Analysis Of Mechanical Exfoliation Of Graphene For Various Fabrication And Automation Techniques, Lance Yarbrough
The Analysis Of Mechanical Exfoliation Of Graphene For Various Fabrication And Automation Techniques, Lance Yarbrough
Mechanical Engineering Undergraduate Honors Theses
Mechanical Exfoliation of Graphene is an often-overlooked portion of the fabrication of quantum devices, and to create more devices quickly, optimizing this process to generate better flakes is critical. In addition, it would be valuable to simulate test pulls quickly, to gain insight on flake quality of various materials and exfoliation conditions. Physical pulls of graphene at various temperatures, pull forces, and pull repetitions were analyzed and compared to the results of ANSYS simulations, solved for similar results. Using ANSYS’ ability to predict trends in exfoliations, flake thickness and coverage using stress and deflection analyses were investigated. Generally, both strongly …
The Analysis Of Mechanical Exfoliation Of Graphene For Various Fabrication And Automation Techniques, Lance Yarbrough
The Analysis Of Mechanical Exfoliation Of Graphene For Various Fabrication And Automation Techniques, Lance Yarbrough
Physics Undergraduate Honors Theses
Mechanical Exfoliation
Analysis And Application Of Finite Element And High-Order Finite Difference Methods For Maxwell’S Equations In Complex Media, Li Zhu
UNLV Theses, Dissertations, Professional Papers, and Capstones
The Perfectly Matched Layer (PML) technique is an effective tool introduced by B´erenger [13] to reduce the unbounded wave propagation problem to a bounded domain problem. This dissertation focuses on two different PML models and their applications to wave propagation problems with Maxwell’s equation in complex media. We investigate these models using two popular numerical methods: the Finite Difference Method (FDM) in Chapters 2 and 3, and the Finite Element Method (FEM) in Chapters 4 and 5.In Chapter 2, we focus on analyzing the stability of a PML developed by B’ecache et al. [10] for simulating wave propagation in the …
Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris
Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris
UNLV Theses, Dissertations, Professional Papers, and Capstones
The nanoscale regime of materials has been at the forefront of research and interest in condensed matter physics for many years. In a merger of the fields of two-dimensional (2D) materials and high pressure physics, we present an investigation of the electronic response of carbon-based, van der Waals (vdW) heterostructures in a diamond anvil cell (DAC). Combining these fields presents us with the ability to study the characteristics of such systems both optically, and through electrical transport. Properties such as conductance, band structure, and layer number are considered. The samples in this study are assembled using exfoliation and stacking techniques …
Design, Fabrication, And Characterization Of An Array Of Graphene Based Variable Capacitors, Millicent Nkirote Gikunda
Design, Fabrication, And Characterization Of An Array Of Graphene Based Variable Capacitors, Millicent Nkirote Gikunda
Graduate Theses and Dissertations
Since it was first isolated and characterized in 2004, graphene has shown the potential for a technological revolution. This is due to its amazing physical properties such as high electrical conductivity, high thermal conductivity, and extreme flexibility. Freestanding graphene membranes naturally possesses an intrinsic rippled structure, and these ripples are in constant random motion even room temperatures. Occasionally, the ripples undergo spontaneous buckling (change of curvature from concave to convex and vice versa) and the potential energy associated with this is a double well potential. This movement of graphene is a potential source of vibrational energy.
In this dissertation, we …
Fabrication And Characterization Of Photodetector Devices Based On Nanostructured Materials: Graphene And Colloidal Nanocrystals, Wafaa Gebril
Graduate Theses and Dissertations
Photodetectors are devices that capture light signals and convert them into electrical signals. High performance photodetectors are in demand in a variety of applications, such as optical communication, security, and environmental monitoring. Among many appealing nanomaterials for novel photodetection devices, graphene and semiconductor colloidal nanocrystals are promising candidates because of their desirable and unique properties compared to conventional materials.
Photodetector devices based on different types of nanostructured materials including graphene and colloidal nanocrystals were investigated. First, graphene layers were mechanically exfoliated and characterized for device fabrication. Self-powered few layers graphene phototransistors were studied. At zero drain voltage bias and room …
Semi-Empirical Modeling Of Liquid Carbon's Containerless Solidification, Philip C. Chrostoski
Semi-Empirical Modeling Of Liquid Carbon's Containerless Solidification, Philip C. Chrostoski
Doctoral Dissertations
“Elemental carbon has important structural diversity, ranging from nanotubes through graphite to diamond. Previous studies of micron-size core/rim carbon spheres extracted from primitive meteorites suggest they formed around such stars via the solidification of condensed carbon-vapor droplets, followed by gas-to-solid carbon coating to form the graphite rims. Similar core/rim particles result from the slow cooling of carbon vapor in the lab. The long-range carbon bond-order potential was used to computationally study liquid-like carbon in (1.8 g/cm3) periodic boundary (tiled-cube supercell) and containerless (isolated cluster) settings. Relaxations via conjugate-gradient and simulated-annealing nucleation and growth simulations using molecular dynamics were …
Synthesis Of Graphene Using Plasma Etching And Atmospheric Pressure Annealing: Process And Sensor Development, Andrew Robert Graves
Synthesis Of Graphene Using Plasma Etching And Atmospheric Pressure Annealing: Process And Sensor Development, Andrew Robert Graves
Graduate Theses, Dissertations, and Problem Reports
Having been theorized in 1947, it was not until 2004 that graphene was first isolated. In the years since its isolation, graphene has been the subject of intense, world-wide study due to its incredibly diverse array of useful properties. Even though many billions of dollars have been spent on its development, graphene has yet to break out of the laboratory and penetrate mainstream industrial applications markets. This is because graphene faces a ‘grand challenge.’ Simply put, there is currently no method of manufacturing high-quality graphene on the industrial scale. This grand challenge looms particularly large for electronic applications where the …
Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias
Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias
Arts & Sciences Electronic Theses and Dissertations
To induce a non-negligible spin-orbit coupling in monolayer graphene, for the purposes of realizing the Kane-Mele Hamiltonian, transition metal adatoms have been deposited in dilute amounts by thermal evaporation in situ while holding the device temperature near 4K. Electronic transport studies including measurements such as gate voltage dependent conductivity and mobility, weak localization, high field magnetoresistance (Shubnikov de Haas oscillations), quantum Hall, and nonlocal voltage were performed at low temperature before and after sequential evaporations. Studies of tungsten adatoms are consistent with literature regarding other metal adatoms on graphene but were unsuccessful in producing a spin-orbit signature, at least partially …
Exploring The Electrical Properties Of Twisted Bilayer Graphene, William Shannon
Exploring The Electrical Properties Of Twisted Bilayer Graphene, William Shannon
Senior Theses
Two-dimensional materials exhibit properties unlike anything else seen in conventional substances. Electrons in these materials are confined to move only in the plane. In order to explore the effects of these materials, we have built apparatus and refined procedures with which to create two-dimensional structures. Two-dimensional devices have been made using exfoliated graphene and placed on gold contacts. Their topography has been observed using Atomic Force Microscopy (AFM) confirming samples with monolayer, bilayer, and twisted bilayer structure. Relative work functions of each have been measured using Kelvin Probe Force Microscopy (KPFM) showing that twisted bilayer graphene has a surface potential …
Plasmonic Properties Of Nanoparticle And Two Dimensional Material Integrated Structure, Desalegn Tadesse Debu
Plasmonic Properties Of Nanoparticle And Two Dimensional Material Integrated Structure, Desalegn Tadesse Debu
Graduate Theses and Dissertations
Recently, various groups have demonstrated nano-scale engineering of nanostructures for optical to infrared wavelength plasmonic applications. Most fabrication technique processes, especially those using noble metals, requires an adhesion layer. Previously proposed theoretical work to support experimental measurement often neglect the effect of the adhesion layers. The first finding of this work focuses on the impact of the adhesion layer on nanoparticle plasmonic properties. Gold nanodisks with a titanium adhesion layer are investigated by calculating the scattering, absorption, and extinction cross-section with numerical simulations using a finite difference time domain (FDTD) method. I demonstrate that a gold nanodisk with an adhesive …
Electron Transport In One And Two Dimensional Materials, Samuel William Lagasse
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, …
Scanning Probe Microscopy Measurements On 2d Materials And Iridates, Armin Ansary
Scanning Probe Microscopy Measurements On 2d Materials And Iridates, Armin Ansary
Theses and Dissertations--Physics and Astronomy
In the past two decades, there has been a quest to understand and utilize novel materials such as iridates and two-dimensional (2D) materials. These classes of materials show a lot of interesting properties both in theoretical predictions as well as experimental results. Physical properties of some of these materials have been investigated using scanning probe measurements, along with other techniques.
One-dimensional (1D) catalytic etching was investigated in few-layer hexagonal boron nitride (hBN) films. Etching of hBN was shown to share several similarities with that of graphitic films. As in graphitic films, etch tracks in hBN commenced at film edges and …
Measuring The Double Layer Capacitance Of Electrolyte Solutions Using A Graphene Field Effect Transistor, Agatha Ulibarri
Measuring The Double Layer Capacitance Of Electrolyte Solutions Using A Graphene Field Effect Transistor, Agatha Ulibarri
Senior Theses
When operating graphene field effect transistors (GFETs) in fluid, a double layer capacitance (Cdl) is formed at the surface. In the literature, the Cdl is estimated using values obtained using metal electrode experiments. Due to the distinctive electronic and surface properties of graphene, there is reason to believe these estimates are inadequate. This work seeks to directly characterize the double layer capacitance of a GFET. A unique method for determining the Cdl has been implemented, and data has been obtained for three electrolytes and one ionic fluid. The results yield dramatically lower Cdl values than …
The Incorporation Of Graphene To Lithium Cobalt Oxide As A Cathode To Improve The Performance Of Lithium Ion Batteries, Kenan Wang
Graduate Theses and Dissertations
One of the objectives of this thesis work was to investigate the cathode performance of lithium cobalt oxide (LiCoO2) incorporated with graphene powder in lithium ion batteries (LIBs). Graphene powder was incorporated into cathode materials to enhance the performance of LIBs. The other objective was to impede the construction of a solid electrolyte interphase (SEI) sheet using graphene sheet coating on its cathode.
The results of this work show that adding graphene powder improved the performance of LiCoO¬2 as a cathode material. With the incorporation of different weight percentages of graphene powder, the LiBs showed distinct changes in their charging …
Surface Energy In Bond-Counting Models On Bravais And Non-Bravais Lattices, Tim Ryan Krumwiede
Surface Energy In Bond-Counting Models On Bravais And Non-Bravais Lattices, Tim Ryan Krumwiede
Doctoral Dissertations
Continuum models in computational material science require the choice of a surface energy function, based on properties of the material of interest. This work shows how to use atomistic bond-counting models and crystal geometry to inform this choice. We will examine some of the difficulties that arise in the comparison between these models due to differing types of truncation. New crystal geometry methods are required when considering materials with non-Bravais lattice structure, resulting in a multi-valued surface energy. These methods will then be presented in the context of the two-dimensional material graphene in a way that correctly predicts its equilibrium …
Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle
Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle
Open Access Theses & Dissertations
A density functional theory (DFT) study on the geometric and electronic structure of C60 and Sc3N@C80 along with their adsorption on pristine single layer graphene (SLG) is presented. C60 is found to adsorb in two nearly degenerate configurations: (i) with a pentagon facing the SLG, which is the most stable one, and (ii) with a hexagon facing the SLG in a face-to-face perfect alignment, rarely common in Ï?â??Ï? interactions, 0.06 eV higher in energy. The calculated binding energy of 0.76 eV, which includes dispersion effects, is in good agreement with previous theoretical and experimental reports. On the contrary, Sc3N@C80 adsorption …
Measuring Nonlinear Properties Of Graphene Thin Films Using Z-Scan Technique, Thekrayat Hassan Al Abdulaal
Measuring Nonlinear Properties Of Graphene Thin Films Using Z-Scan Technique, Thekrayat Hassan Al Abdulaal
Graduate Theses and Dissertations
The nonlinear studies of two-dimensional (2D) nanomaterials, specifically graphene, are very significant since graphene is finding its usefulness in handling the enormous heat in nanoscale high-density power electronics. Graphene has emerged to be a promising nanomaterial as an excellent heat spreader due to its high thermal conductivity. However, the experimental nonlinear study of graphene materials and their application in developing future optoelectronic devices demands for more developed research.
The research objective is first to build a precise, and sensitive technique to investigate and understand the thermal nonlinear properties, including nonlinear refractive index (n2), nonlinear absorption coefficient (β), and thermo-optic coefficient …
Preparation And Characterization Of Van Der Waals Heterostructures, Horacio Coy Diaz
Preparation And Characterization Of Van Der Waals Heterostructures, Horacio Coy Diaz
USF Tampa Graduate Theses and Dissertations
In this dissertation different van der Waals heterostructures such as graphene-MoS2 and MoTe2-MoS2 were prepared and characterized. In the first heterostructure, polycrystalline graphene was synthesized by chemical vapor deposition and transferred on top of MoS2 single crystal. In the second heterostructure, MoTe2 monolayers were deposited on MoS2 by molecular beam epitaxy.
Characterization of graphene-MoS2 heterostructures was conducted by spin and angle resolve spectroscopy which showed that the electronic structure of the bulk MoS2 and graphene in this van der Waals heterostructures is modified. For MoS2 underneath the graphene, a band …
Novel Two-Dimensional Devices For Future Applications, Pratik Agnihotri
Novel Two-Dimensional Devices For Future Applications, Pratik Agnihotri
Legacy Theses & Dissertations (2009 - 2024)
The scalability of field effect transistor has led to the monumental success of complementary metal-oxide-semiconductor (CMOS) technology. In the past, device scaling was not the major issue to a greater extent. Recently with current technology nodes, transistor characteristics show signs of reduced performance due to short channel effects and other issues related to device scaling. Device designers look for innovative ways to enhance the transistor performance while keeping up with device miniaturization. Successful inventions include the development of tri-gate technology, gate all around (GAA) field effect transistors, silicon-on-insulator substrate, and high-k dielectrics. These developments have enabled the device scaling that …
Nano And Nanostructured Materials For Optical Applications, Panit Chantharasupawong
Nano And Nanostructured Materials For Optical Applications, Panit Chantharasupawong
Electronic Theses and Dissertations
Nano and nanostructured materials offer unique physical and chemical properties that differ considerably from their bulk counterparts. For decades, due to their fascinating properties, they have been extensively explored and found to be beneficial in numerous applications. These materials are key components in many cutting-edge optic and photonic technologies, including photovoltaics, waveguides and sensors. In this dissertation, the uses of nano and nanostructured materials for optical applications are investigated in the context of optical limiting, three dimensional displays, and optical sensing. Nanomaterials with nonlinear optical responses are promising candidates for self-activating optical limiters. In the first part of this study, …
Transport And Optical Properties Of Low-Dimensional Complex Systems, Andrii Iurov
Transport And Optical Properties Of Low-Dimensional Complex Systems, Andrii Iurov
Dissertations, Theses, and Capstone Projects
Over the last five years of my research work, I, my research was mainly concerned with certain crucial tunneling, transport and optical properties of novel low-dimensional graphitic and carbon-based materials as well as topological insulators. Both single-electron and many-body problems were addressed. We investigated the Dirac electrons transmission through a potential barrier in the presence of circularly polarized light. An anomalous photon-assisted enhanced transmission is predicted and explained in a comparison with the well-known Klein paradox. It is demonstrated that the perfect transmission for nearly-head-on collision in an infinite graphene is suppressed in gapped dressed states of electrons, which is …
Theoretical Studies Of The Growth And Functionality Of Layered Materials, Wei Chen
Theoretical Studies Of The Growth And Functionality Of Layered Materials, Wei Chen
Doctoral Dissertations
In this thesis, we present several projects on the growth and functionality of layered materials, using density functional theory (DFT) method and phenomenological modeling approach. Beyond the understanding of growth mechanisms and exploration of properties, we propose novel avenues to realize controllable growth processes and layered materials with desirable properties. The contents have three major parts:
(1) Graphene growth on Cu(111) and Ni(111) substrates. We first demonstrate that the inherent multi-orientational degeneracy of the graphene islands on Cu(111) in the early stages of nucleation could result in the prevalence of grain boundaries (GBs). Next, we propose a possible solution to …
Nanoscale Manipulation Of Pristine And Functionalized Freestanding Graphene Using Scanning Tunneling Microscopy, Matthew Ackerman
Nanoscale Manipulation Of Pristine And Functionalized Freestanding Graphene Using Scanning Tunneling Microscopy, Matthew Ackerman
Graduate Theses and Dissertations
Over the past ten years the 2D material graphene has attracted an enourmous amount of attention from researchers from across diciplines and all over the world. Many of its outstanding electronic properties are present only when it is not interacting with a substrate but is instead freestanding. In this work I demonstrate that pristine and functionalized freestanding graphene can be imaged using a scanning tunneling microscope (STM) and that imaging a flexible 2D surface is fundamentally different from imaging a bulk material due to the attraction between the STM tip and the sample. This attraction can be used to manipulate …
Discrete Strain Engineering In Graphene, Cedric Marcus Horvath
Discrete Strain Engineering In Graphene, Cedric Marcus Horvath
Graduate Theses and Dissertations
Graphene has a number of fascinating mechanical and electrical properties. Strain engineering in graphene is the attempt to control its properties with mechanical strain. Previous research in this area has come up with an approach using a continuum theory to describe the strain induced gauge fields in graphene; however, this approach is only valid for small strains (5% at most). A discrete framework is being developed in Arkansas that can more accurately calculate the deformation (electrical) and (pseudo-)magnetic gauge fields created by large strains. Computational simulations were carried out and used to get discrete atomic positions for strained, suspended graphene …
Fundamental Studies Of Supported Graphene Interfaces : Defect Density Of States In Graphene Field Effect Transistors (Fets) And Ideal Graphene - Silicon Schottky Diodes, Dhiraj Sinha
Legacy Theses & Dissertations (2009 - 2024)
The physics of transport in atomically thin 2D materials is an active area of research, important for understanding fundamental properties of reduced dimensional materials and for applications. New phenomena based on graphene may include properties of topologically protected insulators. Applications of these materials are envisioned in electronics, optoelectronics and spintronics.
Growth And Characterization Of Graphene On Cuni Substrates, Parul Tyagi
Growth And Characterization Of Graphene On Cuni Substrates, Parul Tyagi
Legacy Theses & Dissertations (2009 - 2024)
Graphene is a single layer of sp2 bonded carbon atoms that crystallizes in the honeycomb structure. Because of its true two-dimensional structure, it has very unique electrical properties, including a very high carrier mobility that is symmetric for holes and electrons. To realize these unique properties, it is important to develop a method for growing graphene films with uniform thickness and low defect density. One of the most popular methods of growth is by chemical vapor deposition on Cu substrates, because it is self-limited. However many applications require the growth of graphene films that are more than one atomic layer …
Metal Oxide Growth, Spin Precession Measurements And Raman Spectroscopy Of Cvd Graphene, Akitomo Matsubayashi
Metal Oxide Growth, Spin Precession Measurements And Raman Spectroscopy Of Cvd Graphene, Akitomo Matsubayashi
Legacy Theses & Dissertations (2009 - 2024)
The focus of this dissertation is to explore the possibility of wafer scale graphene-based spintronics. Graphene is a single atomic layer of sp2 bonded carbon atoms that has attracted much attention as a new type of electronic material due to its high carrier mobilities, superior mechanical properties and extremely high thermal conductivity. In addition, it has become an attractive material for use in spintronic devices owing to its long electron spin relaxation time at room temperature. This arises in part from its low spin-orbit coupling and negligible nuclear hyperfine interaction. In order to realize wafer scale graphene spintronics, utilization of …
Electron Correlation Effects In Strained Dual-Layer Graphene Systems, Peter Karl Harnish
Electron Correlation Effects In Strained Dual-Layer Graphene Systems, Peter Karl Harnish
Graduate College Dissertations and Theses
In low dimensional systems, electron correlation effects can often be enhanced. This can be vital since these effects not only play an important role in the study of many-electron physics, but are also useful in designing new materials for various applications. Since its isolation from graphite in 2004, graphene, a two dimensional sheet of carbon atoms, has drawn considerable interest due to its remarkable properties. In the past few years, research has moved on from single to bi-, dual- and multi-layer graphene systems, each displaying their own multitudes of intriguing properties. In particular, multi-layer systems that are electronically decoupled, but …