Physical Sciences and Mathematics Commons^™

Electrostatic Force Microscopy And Electrical Isolation Of Etched Few-Layer Graphene Nano-Domains, D. Patrick Hunley, Abhishek Sundararajan, Mathias J. Boland, Douglas R. Strachan

Physics and Astronomy Faculty Publications

Nanostructured bi-layer graphene samples formed through catalytic etching are investigated with electrostatic force microscopy. The measurements and supporting computations show a variation in the microscopy signal for different nano-domains that are indicative of changes in capacitive coupling related to their small sizes. Abrupt capacitance variations detected across etch tracks indicates that the nano-domains have strong electrical isolation between them. Comparison of the measurements to a resistor-capacitor model indicates that the resistance between two bi-layer graphene regions separated by an approximately 10 nm wide etch track is greater than about 1×10¹² Ω with a corresponding gap resistivity greater than about …

Collective Edge Modes Near The Onset Of A Graphene Quantum Spin Hall State, Gunpathy Murthy, Efrat Shimshoni, H. A. Fertig

Physics and Astronomy Faculty Publications

Graphene subject to a strong, tilted magnetic field exhibits an insulator-metal transition tunable by tilt angle, attributed to the transition from a canted antiferromagnetic (CAF) to a ferromagnetic (FM) bulk state at filling factor ν=0. We develop a theoretical description for the spin and valley edge textures in the two phases, and the implied evolution in the nature of edge modes through the transition. In particular, we show that the CAF has gapless neutral modes in the bulk, but supports gapped charged edge modes. At the transition to the FM state the charged edge modes become gapless and are …

Kelvin Probe Force Microscopy On Graphene Thin Films For Solar Cell And Biosensing Applications, Faranak Sharifi

Electronic Thesis and Dissertation Repository

Graphene, a one atom thick planer sheet of carbon atoms, has attracted much attention in scientific and technological communities due to its remarkable electronic and physical properties. Graphene has been widely studied as an alternative to transparent conducting Indium Tin Oxide (ITO) electrodes in organic photovoltaics fabrication. Graphene platforms have also attracted interest in biological applications. However, large area graphene films are not yet widely commercialized because the fabrication techniques needed to prepare high quality graphene are expensive and non-scalable. More importantly, most of the low cost fabrication techniques require using toxic materials, which are not biocompatible for using graphene …

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

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

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 …

Binding Of Solvated Peptide (Eplqlkm) With A Graphene Sheet Via Simulated Coarse-Grained Approach, Somayyeh Sheikholeslami, R. B. Pandey, Nadiya Dragneva, Wely Floriano, Oleg Rubel, Stephen A. Barr, Zhifeng Kuang, Rajiv Berry, Rajesh Naik, Barry Farmer

Faculty Publications

Binding of a solvated peptide A1 (¹E ²P ³L ⁴Q ⁵L ⁶K ⁷M) with a graphene sheet is studied by a coarse-grained computer simulation involving input from three independent simulated interaction potentials in hierarchy. A number of local and global physical quantities such as energy, mobility, and binding profiles and radius of gyration of peptides are examined as a function of temperature (T). Quantitative differences (e.g., the extent of binding within a temperature range) and qualitative similarities are observed in results from three simulated potentials. Differences in variations of both local and …

Optimization Of Chemical Vapor Deposition Grown Graphene, Andrew Tan

Senior Theses

Graphene can be used as the active film in a gas sensor. To provide the best possible electrical properties, it is important that graphene films be single-layered and single-crystalline. A low vacuum chemical vapor deposition (CVD) chamber was constructed to grow graphene with these properties. The effect of growth parameters, such as annealing times and methane partial pressure, on the quality of graphene was investigated. Raman spectra of graphene were used to quantify the characteristics of the synthesized graphene. Graphene synthesized through CVD has two major peaks, the G (~1570cm^-1) and the 2D peak (~2700 cm^-1). …

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 …

Atomic-Scale Characterization And Manipulation Of Freestanding Graphene Using Adapted Capabilities Of A Scanning Tunneling Microscope, Steven Barber

Graduate Theses and Dissertations

Graphene was the first two-dimensional material ever discovered, and it exhibits many unusual phenomena important to both pure and applied physics. To ensure the purest electronic structure, or to study graphene's elastic properties, it is often suspended over holes or trenches in a substrate. The aim of the research presented in this dissertation was to develop methods for characterizing and manipulating freestanding graphene on the atomic scale using a scanning tunneling microscope (STM). Conventional microscopy and spectroscopy techniques must be carefully reconsidered to account for movement of the extremely flexible sample.

First, the acquisition of atomic-scale images of freestanding graphene …

Electronic Properties And Atomic Scale Microscopy Of Two Dimensional Materials: Graphene And Molybdenum Disulfide, Jyoti Katoch

Electronic Theses and Dissertations

Novel two dimensional nanoscale materials like graphene and metal dichalcogenides (MX2) have attracted the attention of the scientific community, due to their rich physics and wide range of potential applications. It has been shown that novel graphene based transparent conductors and radiofrequency transistors are competitive with the existing technologies. Graphene’s properties are influenced sensitively by adsorbates and substrates. As such not surprisingly, physical properties of graphene are found to have a large variability, which cannot be controlled at the synthesis level, reducing the utility of graphene. As a part of my doctorate dissertation, I have developed atomic hydrogen as a …

Dynamical Spin Injection In Graphene, Simranjeet Singh

Electronic Theses and Dissertations

Within the exciting current trend to explore novel low-dimensional systems, the possibility to inject pure spin currents in graphene and other two-dimensional crystals has attracted considerable attention in the past few years. The theoretical prediction of large spin relaxation times and experimentally observed mesoscopic-scale spin diffusion lengths places graphene as a promising base system for future spintronics devices. This is due to the unique characteristics intrinsic to the two-dimensional lattice of carbon atoms forming graphene, such as the lack of nuclear spins and weak spin-orbit coupling of the charge carriers. Interestingly for some spintronic applications, the latter can be chemically …

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 …

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

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

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 …