Physics Commons^™

Synthesis, Characterization, And Simulation Of Two-Dimensional Materials, Lawrence Hudy

Theses and Dissertations

ABSTRACT

SYNTHESIS, CHARACTERIZATION, AND SIMULATION OF TWO-DIMENSIONAL MATERIALS

by

Lawrence Hudy

The University of Wisconsin-Milwaukee, 2023Under the Supervision of Professor Michael Weinert

This dissertation focuses on my journey through many aspects of surface science leading to the first principles investigation of transition metal dichalcogenides studying the impact of defects, twist, and decreasing interlayer separation to probe their effect on the electronic properties of these materials. My journey started out learning many aspects of material science such as methods for material synthesis and characterization but later ended on simulation of material properties using density functional theory. In the first experiments, we …

A Study Of Single Molecule Detection With Graphene Hall Bars, Kenneth Stephen Stephenson

Theses and Dissertations

In 2007, detection of individual molecules with a solid-state gas sensor was reported for first time by Schedin et al. where they used micromechanically-cleaved graphene for their sensing material, which exhibits isotropic and homogeneous conduction [1]. However, despite the novelty and popularity of their work, it has never been repeated. Further, we found their associated calculations to be self-inconsistent by a factor of 103 . So, hoping to account for and resolve this discrepancy, we outline the plan we had to reproduce their experiment. We also justify any substantial modifications, particularly our choice to use epitaxial graphene instead. Then, we …

Spatial Inhomogeneous Barrier Heights At Graphene/Semiconductor Schottky Junctions, Dushyant Tomer

Theses and Dissertations

Graphene, a semimetal with linear energy dispersion, forms Schottky junction when interfaced with a semiconductor. This dissertation presents temperature dependent current-voltage and scanning tunneling microscopy/spectroscopy (STM/S) measurements performed on graphene Schottky junctions formed with both three and two dimensional semiconductors.

To fabricate Schottky junctions, we transfer chemical vapor deposited monolayer graphene onto Si- and C-face SiC, Si, GaAs and MoS2 semiconducting substrates using polymer assisted chemical method. We observe three main type of intrinsic spatial inhomogeneities, graphene ripples, ridges and semiconductor steps in STM imaging that can exist at graphene/semiconductor junctions. Tunneling spectroscopy measurements reveal fluctuations in graphene Dirac point …

Tunneling Experiments With Dirac Electrons In Graphene Heterojunctions, Shivani Rajput

Theses and Dissertations

This dissertation presents results of scanning tunneling microscopy/spectroscopy experiments performed on graphene, a two-dimensional membrane of carbon atoms arranged in a honeycomb lattice, where charge carriers behave like massless fermions described by the Dirac equation. Our findings demonstrate that interface engineering is a viable route to control and further enhance the electronic properties of graphene.

In the first experiment, by transferring chemical vapor deposited (CVD) graphene onto substrates of opposite polarization - H-terminated Si-face and C-faces of hexagonal silicon carbide (SiC), we show that the type of charge carrier in graphene can be controlled by substrate polarization. Furthermore, we find …

Probing Bonding And Dynamics At Heterogeneous Adsorbate/Graphene Interfaces, Eric Charles Mattson

Theses and Dissertations

Graphene-based materials are becoming an astoundingly promising choice for many relevant technological and environmental applications. Deriving graphene from the reduction of graphene oxide (GO) is becoming a popular and inexpensive route toward the synthesis of these materials. While the desired product from GO reduction is pristine graphene, defects and residual oxygen functional groups inherited from the parent GO render reduced graphene oxide (RGO) distinct from graphene. In this work, the structure and bonding for GO and RGO is investigated to the end of a working understanding of the composition and properties of these materials. In situ selected area electron diffraction …

Nanoscale Surface Patterning And Applications: Using Top-Down Patterning Methods To Aid Bottom-Up Fabrication, Anthony Craig Pearson

Theses and Dissertations

Bottom-up self-assembly can be used to create structures with sub-20 nm feature sizes or materials with advanced electrical properties. Here I demonstrate processes to enable such self-assembling systems including block copolymers and DNA origami, to be integrated into nanoelectronic devices. Additionally, I present a method which utilizes the high stability and electrical conductivity of graphene, which is a material formed using a bottom-up growth process, to create archival data storage devices. Specifically, I show a technique using block copolymer micelle lithography to fabricate arrays of 5 nm gold nanoparticles, which are chemically modified with a single-stranded DNA molecule and used …