Electronic Transport In Few Layer Graphene

Author : Brian Bersch
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (113 download)

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Download or read book Electronic Transport in Synthetic Transition Metal Dichalcogenides and Novel Graphene/metal Heterostructures written by Brian Bersch and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional (2D) and layered materials are atomically thin sheets of materials whose monolayer forms range from single to few atoms in thickness and which display fundamentally anisotropic bonding configurations characterized by strong in-plane (intralayer) bonding and weak out-of-plane (interlayer) van der Waals bonding. Pristine 2D materials lack dangling bonds and are inherently thickness-scalable, representing the thinnest stable material systems in science. Additionally, the 2D materials sandbox encompasses the entire range of electronic classification of materials from insulators to semiconductors to conductors (and superconductors) and are also truly quantum in nature. Thus, 2D materials and their heterostructures are poised to revolutionize conventional electronics, optoelectronics, and quantum technologies. In order to demonstrate technological readiness, however, 2D materials must be synthesized on the wafer-scale with ultimate control over film properties, defects, film morphology, and thickness. In a similar vein, 2D-superconductors will be essential components in future quantum devices, and they will also need to be synthesized and integrated into robust wafer-scale platforms if they are to become technologically relevant. Over the years, the Robinson group has been a pioneer in the metal organic chemical vapor deposition of transition metal dichalcogenides (TMDs) for realization of large-area and scalable electronic-grade 2D-semiconductors, as well as the synthesis of wafer-scale epitaxial graphene (EG) on SiC. This thesis is fundamentally about understanding the electronic transport of charge carriers in synthetic two-dimensional layers and graphene-based heterostructures, elucidated by field-effect transistor and other electrical measurements and correlated to materials characterization of as-grown films. We strive to understand the impact of growth substrate, growth conditions, and dopants on the electronic properties of epitaxial 2D-semiconductors including molybdenum disulfide (MoS2) and tungsten disulfide (WSe2). Additionally, we have pioneered a new synthesis technique for stabilizing 2D-allotropes of traditionally 3D metals and nitrides at the interface of epitaxial graphene and SiC in a process termed confinement heteroepitaxy (CHet). These graphene/2D-metal heterostructures are inherently air-stable, highly crystalline, non-centrosymmetric, and exhibit the potential for tunable superconductivity, topological states, and extreme non-linear optical properties. As a result, this thesis is broken up into two main sections. First, after a short introduction to 2D-materials, devices and procedures (Chapters 1-2), chapters 3-5 investigate the transport and transistor performance in single to few-layer MoS2 and WSe2 synthesized on engineered sapphire substrates, including a novel technique for the selective-area deposition and growth of TMDs in chapter 5. Chapter 6 introduces the concept of confinement heteroepitaxy and discusses the optimization of this process to achieve large-area uniform EG/2D-Ga and EG/GaN heterostructures. Within, we discuss the structure and material properties of 2D-Ga films at the interface of graphene and SiC, and we discuss considerations and impacts of the nitridation process on graphene overlayers. Chapter 7 specifically deals with the superconductivity in these graphene/2D-Ga heterostructures and helps to shed light on the origin of the critical temperature (Tc) enhancement in hexagonal 2D-Ga/SiC. Chapter 8 will present ongoing and future work with a summary of findings in this thesis.