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Plasma Based Synthesis And Surface Modification Of Graphene., Rong Zhao

Electronic Theses and Dissertations

Graphene, an atom thick layer of carbon, has attracted intense scientific interest due to its exceptional electrical, mechanical and chemical properties. Especially, it provides a perfect platform to explore the unique electronic properties in absolute two-dimension. Pristine graphene possesses zero band gap and weakens its competitiveness in the field of semiconductors. In order to induce a band gap and control its semiconducting properties, functionalization and doping are two of the most feasible methods. In the context of functionalization, large area monolayer graphene synthesized by chemical vapor deposition was subjected to controlled and sequential fluorination using radio frequency plasma while monitoring …

Computational Modeling Of Defect-Engineered Graphene Derivatives And Graphene-Polymer Nanocomposites, Asanka Weerasinghe

Doctoral Dissertations

Graphene has unique mechanical, electronic, and thermal properties, which enable a broad range of technological applications. For example, graphene flakes can be used as filler to enhance the properties of polymer-matrix nanocomposites and graphene derivatives, generated by defect engineering and chemical functionalization of single-layer graphene, have tunable properties that are very promising for engineering electronic and thermomechanical metamaterials. A fundamental understanding of the structure-property relationships that govern the function of such nanocomposites and graphene derivatives is required for designing and developing future graphene-based metamaterials. Toward this end, we have conducted a systematic study based on extensive molecular-dynamics simulations of mechanical …

Antenna Enhanced Graphene Terahertz Emitter And Detector, And Graphene Microwave Detector, Jiayue Tong

Doctoral Dissertations

Graphene is a promising candidate for optoelectronic and fast electronics research. In THz and sub-THz frequency regime, sensitive detectors are very difficult to make. This dissertation presents my Ph.D study of THz sources and THz/Microwave (MW) detectors made with graphene. My work demonstrates the emission and detection of 1.9 THz radiation from graphene coupled to a double-patch antenna and a silicon lens. More than 3 orders of magnitude performance improvements are achieved in a half-edge-contacted graphene thermoelectric (TE) detector operating at 1.9 THz by antenna coupling and Si lens coupling. The thermoelectric mechanism is also employed in MW detection. A …

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 (C_dl) is formed at the surface. In the literature, the C_dl 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 C_dl has been implemented, and data has been obtained for three electrolytes and one ionic fluid. The results yield dramatically lower C_dl 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 …

Two Stream Instability In Graphene, Mitchell Duffer

Williams Honors College, Honors Research Projects

Mitchell Duffer

Major: Physics

Project Sponsor: Ben Yu-Kuang Hu

Number of Project Credits: 2

Two Stream Instability in Graphene

We investigate the unstable modes of the two-stream instability in graphene to determine if they can occur. This instability occurs when a population of electrons streams past another inside graphene. We obtain the unstable modes by numerically determining the zeros of the non-equilibrium graphene dielectric function using MATLAB. The dielectric function used in this study, in contrast to previous studies, includes the effects of the particle-hole excitation continuum (PHEC) that normally quells the evolution of unstable plasmons. MATLAB’s built in zero …

Nanoscale Devices Consisting Of Heterostructures Of Carbon Nanotubes And Two-Dimensional Layered Materials, Mohsen Nasseri

Theses and Dissertations--Physics and Astronomy

One dimensional carbon nanotubes (CNTs) and two-dimensional layered materials like graphene, MoS₂, hexagonal boron nitride (hBN), etc. with different electrical and mechanical properties are great candidates for many applications in the future. In this study the synthesis and growth of carbon nanotubes on both conducting graphene and graphite substrates as well as insulating hBN substrate with precise crystallographic orientation is achieved. We show that the nanotubes have a clear preference to align to specific crystal directions of the underlying graphene or hBN substrate. On thicker flakes of graphite, the edges of these 2D materials can control the orientation …