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Investigation Of Two Dimensional Transition Metal Dichalcogenides By Optical And Scanning Tunneling Spectroscopy
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Book Synopsis Investigation of Two-Dimensional Transition Metal Dichalcogenides by Optical and Scanning Tunneling Spectroscopy by :
Download or read book Investigation of Two-Dimensional Transition Metal Dichalcogenides by Optical and Scanning Tunneling Spectroscopy written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The latter portion of this dissertation will cover the nanoscopic dynamics of TMDC heterostructures. The Kramers-Kronig relations will be derived and discussed in detail. Data and results regarding the electronic structure of these materials, their heterostructures, and their custom alloys measured via scanning tunneling microscopy will be presented. Coupled with the measured optical properties, significant numerical quantities that characterize these materials are extracted. There will be several appendices that offer some supplementary information and basic summaries about all the projects that were initiated.
Book Synopsis Two-Dimensional Transition-Metal Dichalcogenides by : Alexander V. Kolobov
Download or read book Two-Dimensional Transition-Metal Dichalcogenides written by Alexander V. Kolobov and published by Springer. This book was released on 2016-07-26 with total page 545 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes the current status of theoretical and experimental progress in 2 dimensional graphene-like monolayers and few-layers of transition metal dichalcogenides (TMDCs). Semiconducting monolayer TMDCs, due to the presence of a direct gap, significantly extend the potential of low-dimensional nanomaterials for applications in nanoelectronics and nano-optoelectronics as well as flexible nano-electronics with unprecedented possibilities to control the gap by external stimuli. Strong quantum confinement results in extremely high exciton binding energies which forms an interesting platform for both fundamental studies and device applications. Breaking of spatial inversion symmetry in monolayers results in strong spin-valley coupling potentially leading to their use in valleytronics. Starting with the basic chemistry of transition metals, the reader is introduced to the rich field of transition metal dichalcogenides. After a chapter on three dimensional crystals and a description of top-down and bottom-up fabrication methods of few-layer and single layer structures, the fascinating world of two-dimensional TMDCs structures is presented with their unique atomic, electronic, and magnetic properties. The book covers in detail particular features associated with decreased dimensionality such as stability and phase-transitions in monolayers, the appearance of a direct gap, large binding energy of 2D excitons and trions and their dynamics, Raman scattering associated with decreased dimensionality, extraordinarily strong light-matter interaction, layer-dependent photoluminescence properties, new physics associated with the destruction of the spatial inversion symmetry of the bulk phase, spin-orbit and spin-valley couplings. The book concludes with chapters on engineered heterostructures and device applications such as a monolayer MoS2 transistor. Considering the explosive interest in physics and applications of two-dimensional materials, this book is a valuable source of information for material scientists and engineers working in the field as well as for the graduate students majoring in materials science.
Book Synopsis Two-Dimensional Transition-Metal Dichalcogenides by : Chi Sin Tang
Download or read book Two-Dimensional Transition-Metal Dichalcogenides written by Chi Sin Tang and published by John Wiley & Sons. This book was released on 2023-11-08 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-Dimensional Transition-Metal Dichalcogenides Comprehensive resource covering rapid scientific and technological development of polymorphic two-dimensional transition-metal dichalcogenides (2D-TMDs) over a range of disciplines and applications Two-Dimensional Transition-Metal Dichalcogenides: Phase Engineering and Applications in Electronics and Optoelectronics provides a discussion on the history of phase engineering in 2D-TMDs as well as an in-depth treatment on the structural and electronic properties of 2D-TMDs in their respective polymorphic structures. The text addresses different forms of in-situ synthesis, phase transformation, and characterization methods for 2D-TMD materials and provides a comprehensive treatment of both the theoretical and experimental studies that have been conducted on 2D-TMDs in their respective phases. Two-Dimensional Transition-Metal Dichalcogenides includes further information on: Thermoelectric, fundamental spin-orbit structures, Weyl semi-metallic, and superconductive and related ferromagnetic properties that 2D-TMD materials possess Existing and prospective applications of 2D-TMDs in the field of electronics and optoelectronics as well as clean energy, catalysis, and memristors Magnetism and spin structures of polymorphic 2D-TMDs and further considerations on the challenges confronting the utilization of TMD-based systems Recent progress of mechanical exfoliation and the application in the study of 2D materials and other modern opportunities for progress in the field Two-Dimensional Transition-Metal Dichalcogenides provides in-depth review introducing the electronic properties of two-dimensional transition-metal dichalcogenides with updates to the phase engineering transition strategies and a diverse range of arising applications, making it an essential resource for scientists, chemists, physicists, and engineers across a wide range of disciplines.
Book Synopsis Optical Study on Two Dimensional Transition Metal Dichalcogenides by : Bairen Zhu
Download or read book Optical Study on Two Dimensional Transition Metal Dichalcogenides written by Bairen Zhu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Optical Study on Two Dimensional Transition Metal Dichalcogenides" by Bairen, Zhu, 朱柏仁, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Atomically thin group-VI transition metal dichalcogenides (TMDC) has been emerging as a family of intrinsic 2-dimensional (2D) crystals with a sizeable bandgap in the visible and near infrared range, satisfying numerous requirements for ultimate electronics and optoelectronics. This intrinsic 2D crystal also provides a perfect platform for physics study in 2D semiconductors. The characteristic inversion symmetry breaking presented in monolayer TMDCs leads to non-zero but contrasting Berry curvatures and orbital magnetic moments at K/K' valleys located at the corners of the first Brillouin zone. These features provide an opportunity to manipulate electrons' additional internal degrees of freedom, namely the valley degree of freedom, making monolayer TMDC a promising candidate for the conceptual valleytronics. Besides, the strong spin-orbit interactions and the subsequent spin-valley coupling demonstrated in 2D TMDCs open potential new routes towards quantum manipulation. In this thesis, I give a brief review on the background and our progress of the physics study in 2D TMDCs (MoS2, WS2) via optical spectroscopy. Particularly, our experimental approach on the excitonic effect, valley dependent circular dichroism, and the spin-valley coupling in monolayer and bilayer TMDCs are elaborated in individual chapters. DOI: 10.5353/th_b5351031 Subjects: Transition metal compounds - Optical properties Chalcogenides - Optical properties
Book Synopsis Two-Dimensional Transition-Metal Dichalcogenides by : Chi Sin Tang
Download or read book Two-Dimensional Transition-Metal Dichalcogenides written by Chi Sin Tang and published by John Wiley & Sons. This book was released on 2023-11-14 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-Dimensional Transition-Metal Dichalcogenides Comprehensive resource covering rapid scientific and technological development of polymorphic two-dimensional transition-metal dichalcogenides (2D-TMDs) over a range of disciplines and applications Two-Dimensional Transition-Metal Dichalcogenides: Phase Engineering and Applications in Electronics and Optoelectronics provides a discussion on the history of phase engineering in 2D-TMDs as well as an in-depth treatment on the structural and electronic properties of 2D-TMDs in their respective polymorphic structures. The text addresses different forms of in-situ synthesis, phase transformation, and characterization methods for 2D-TMD materials and provides a comprehensive treatment of both the theoretical and experimental studies that have been conducted on 2D-TMDs in their respective phases. Two-Dimensional Transition-Metal Dichalcogenides includes further information on: Thermoelectric, fundamental spin-orbit structures, Weyl semi-metallic, and superconductive and related ferromagnetic properties that 2D-TMD materials possess Existing and prospective applications of 2D-TMDs in the field of electronics and optoelectronics as well as clean energy, catalysis, and memristors Magnetism and spin structures of polymorphic 2D-TMDs and further considerations on the challenges confronting the utilization of TMD-based systems Recent progress of mechanical exfoliation and the application in the study of 2D materials and other modern opportunities for progress in the field Two-Dimensional Transition-Metal Dichalcogenides provides in-depth review introducing the electronic properties of two-dimensional transition-metal dichalcogenides with updates to the phase engineering transition strategies and a diverse range of arising applications, making it an essential resource for scientists, chemists, physicists, and engineers across a wide range of disciplines.
Book Synopsis Two Dimensional Transition Metal Dichalcogenides by : Narayanasamy Sabari Arul
Download or read book Two Dimensional Transition Metal Dichalcogenides written by Narayanasamy Sabari Arul and published by Springer. This book was released on 2019-07-30 with total page 355 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents advanced synthesis techniques adopted to fabricate two-dimensional (2D) transition metal dichalcogenides (TMDs) materials with its enhanced properties towards their utilization in various applications such as, energy storage devices, photovoltaics, electrocatalysis, electronic devices, photocatalysts, sensing and biomedical applications. It provides detailed coverage on everything from the synthesis and properties to the applications and future prospects of research in 2D TMD nanomaterials.
Book Synopsis Optical Study on Two Dimensional Transition Metal Dichalcogenides by : 朱柏仁
Download or read book Optical Study on Two Dimensional Transition Metal Dichalcogenides written by 朱柏仁 and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Defects in Two-Dimensional Materials by : Rafik Addou
Download or read book Defects in Two-Dimensional Materials written by Rafik Addou and published by Elsevier. This book was released on 2022-02-14 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Defects in Two-Dimensional Materials addresses the fundamental physics and chemistry of defects in 2D materials and their effects on physical, electrical and optical properties. The book explores 2D materials such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMD). This knowledge will enable scientists and engineers to tune 2D materials properties to meet specific application requirements. The book reviews the techniques to characterize 2D material defects and compares the defects present in the various 2D materials (e.g. graphene, h-BN, TMDs, phosphorene, silicene, etc.). As two-dimensional materials research and development is a fast-growing field that could lead to many industrial applications, the primary objective of this book is to review, discuss and present opportunities in controlling defects in these materials to improve device performance in general or use the defects in a controlled way for novel applications. Presents the theory, physics and chemistry of 2D materials Catalogues defects of 2D materials and their impacts on materials properties and performance Reviews methods to characterize, control and engineer defects in 2D materials
Book Synopsis Two-dimensional Transition Metal Dichalcogenides by : Tianyi Zhang
Download or read book Two-dimensional Transition Metal Dichalcogenides written by Tianyi Zhang and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are an emerging family of 2D materials beyond graphene. 2D semiconducting TMDs possess a series of unique structural and functional properties, such as the presence of atomically flat surfaces without dangling bonds, layer-dependent electronic band structure, and pronounced excitonic effects, thus making them very intriguing both fundamentally and technologically. Apart from these excellent properties, another important feature of 2D TMDs is that these materials are extremely "tunable". For example, the physicochemical properties of TMDs can be effectively modulated by lattice defects (e.g., vacancies, dopants, grain boundaries) and external perturbations (e.g., strain, substrate effect, van der Waals heterostacks), providing rich opportunities for materials engineers to tailor TMD properties by means of doping, alloying, coupling TMDs with predesigned substrates, etc. Therefore, the research presented in my thesis mainly focuses on the synthesis of 2D semiconducting TMDs, the investigation of their intrinsic defects, and the development of effective substitutional doping and material transfer techniques to engineer their properties for functional applications. Chapter 1 provides an introduction to structures, properties, synthesis techniques, and defect engineering of 2D TMDs. In Chapter 2, two different additive-mediated chemical vapor deposition (CVD) approaches, involving sodium bromide and sodium cholate powders as growth promoters, are demonstrated. Pristine TMDs, alloyed MoxW1-xS2, and in-plane MoxW1-xS2-WxMo1-xS2 heterostructures are synthesized using our methods with improved grain size, yield, and reproducibility when compared to the conventional solid precursor CVD approach. Chapter 3 studies intrinsic defects and their distributions within CVD-synthesized TMD monolayers utilizing a combination of various microscopic and spectroscopic characterization techniques. The results indicate that 3d- and 4d-transition metal impurities (e.g., Cr, Fe, V, Mo) are often nonuniformly distributed within single-crystalline WS2 monolayers, leading to the photoluminescence inhomogeneity that is common in WS2. In addition, scanning tunneling microscopy/spectroscopy studies of CVD-grown WS2 have also unambiguously identified carbon-hydrogen (CH) complex as a common type of intrinsic defects. Chapter 4 reports an effective, convenient, and generalized method for in situ substitutional doping of 2D TMDs. This method is based on spin-coating and high-temperature chalcogenization of a mixture of water-soluble host precursor, dopant precursor, and growth promoter. Using this liquid phase precursor-assisted CVD method, we demonstrate the successful growth of Fe-doped WS2, Re-doped MoS2, and more complex structures such as V-doped in-plane MoxW1-xS2-WxMo1-xS2 heterostructures. In Chapter 5, we develop a clean and deterministic transfer method of 2D TMDs. We report a cellulose acetate-assisted method that transfers TMDs onto various substrates with improved micro- and nano-scale cleanliness. A deterministic transfer system is built up for placing a selected monolayer TMD to target locations on the substrate. The development of 2D TMD transfer techniques facilitates the investigation of their functional applications. As an example, the fabrication and ionic transport properties of monolayer MoS2 nanopore arrays are demonstrated in Chapter 5, and the correlation between ionic conductance and nanopore diameter distributions is carefully analyzed by combined experimental studies and molecular dynamic simulations. Finally, we provide a summary of main findings in this thesis and an outlook of future directions that can be pursued.
Book Synopsis Synthesis of Graphene and Two Dimensional Transitional Metal Dichalcogenides and Their Optical Properties by : Simin Feng
Download or read book Synthesis of Graphene and Two Dimensional Transitional Metal Dichalcogenides and Their Optical Properties written by Simin Feng and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the first isolation of graphene from graphite in 2004, there has been a significant amount of research dedicated to two-dimensional (2D) materials. Graphene is arguably the most famous material which displays remarkable mechanical, thermal and optical properties. However, its lack of an electronic bandgap, limits its application in many areas. Transition metal dichalcogenides (TMDs) such as WSe2, WS2, and MoS2 are another kind of 2D material with semiconducting character. Its direct band-gap feature and favorable electronic and mechanical properties, complement graphene, leading to applications in high-end electronic and optoelectronic applications. This dissertation explores the optical properties of these 2D materials by Raman spectroscopy and their potential applications in molecular sensing have been explored. Chapter 1 provides a brief introduction of various 2D materials, including graphene and TMDs. Crystal structure as well as electronic band structures for these materials have been introduced together with some potential applications of the 2D materials. Chapter 2 gives an introduction on Raman spectroscopy. As one of the heavily used characteristic techniques to probe the optical properties of 2D materials, Raman scattering processes are studied from both macroscopic and microscopic approaches. In addition, normal Raman spectra of 2D materials are measured and by analyzing the Raman spectra, various information about the sample, such as crystallinity, thickness, doping and strain could be obtained indicating Raman can serve as a powerful tool to study properties of 2D materials. In chapter 3, nitrogen-doped (NG) and silicon-doped (SiG) graphene are successfully synthesized through a chemical vapor deposition (CVD) setup. A variety of techniques, including transmission electron microscopy (TEM), scanning tunneling microscopy and spectroscopy (STM/STS), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy are used to characterize the sample and discover how nitrogen and silicon atoms are incorporated into the graphene lattice. Chapter 4 demonstrates that when graphene monolayers are used as substrates to probe the Raman signal of various dye molecules, such as rhodamine B (RhB), crystal violet (CRV) and methylene blue (MB), intensities of the Raman signals from the dye molecules enhance a lot, giving the term as graphene-enhanced Raman scattering effect (GERS). In addition, NG exhibits an extraordinary sensing properties when compared to PG sheets. For example, the Raman vibrational modes of these particular dye molecules can be detected for concentrations as low as 10-11 mol/L and very close to single molecule detection limit. This is the lowest ever reported value when using graphene as a substrate so far. Electronic structure calculations and the simulation of the Raman spectra, performed by our collaborator Dr. Maria Cristina dos Santos from Brazil, suggests that a charge transfer excitation and the proper aligning of the HOMO-LUMO gap of the molecules with respect to the Fermi level of graphene are the key reasons for this enhancement.. Chapter 5 demonstrated that Raman spectroscopy could be a significant tool to study 2D materials by two simple examples. By applying polarized Raman techniques, a new Raman active peak, which is associated with first-order out-of-plane vibrational mode in TMDs is observed. Further experiments and calculations demonstrate that this peak only exist in few layer TMDs materials and does not show in monolayer or bulk samples. The unique property of this mode could potentially provide an easy method to distinguish monolayer TMDs sample just by Raman measurements. Another example is that a mono-dispersed, flower-like MoSe2 nanostructures have been synthesized by colloidal methods by our collaborator (Dr. Shaacks group). This 3D structure contains 2D-quasi-like MoSe2 nanosheets that protrude outwards from a dense central core. Laser power dependent Raman and temperature dependent Raman measurements demonstrate that the interlayer decoupling of these nanosheets could be easily tuned, providing insights on how to modulate the optical properties of TMD materials. Finally, chapter 6 summarizes the studies discussed in this dissertation and provide some perspectives to the potential future works.
Book Synopsis GROWTH OF TRANSITION METAL DIC by : Lu Jiao
Download or read book GROWTH OF TRANSITION METAL DIC written by Lu Jiao and published by Open Dissertation Press. This book was released on 2017-01-26 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Growth of Transition Metal Dichalcogenide Thin Films by Molecular Beam Epitaxy" by Lu, Jiao, 焦璐, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Atomically thin transition metal dichalcogenides (TMD) have attracted intensive research interests due to their extraordinary properties and potential applications in electronics and optoelectronics. In this thesis, epitaxial growths of two-dimensional (2D) MoSe2 and WSe2 thin films were carried out in Molecular Beam Epitaxy (MBE). Multiple characterization techniques were employed to investigate thin films' structural, morphological, electronic and optical properties. A series of submonolayer MoSe2 coverage samples have been grown on highly ordered pyrolytic graphite (HOPG) substrate. Growth temperature and post-growth annealing temperature were seen to have obvious impacts on film's morphology and crystal quality. Layer-by-layer growth mode has been identified for the Van der Waals epitaxy of MoSe2 on HOPG. Dense networks of inversion domain boundaries (IDBs) have been observed in as-grown MoSe2 epifilms by scanning tunneling microscopy (STM) and transmission electron microscopy (TEM), and their density can be tuned by changing the MBE conditions. Scanning tunneling spectroscopy (STS) measurements reveal mid-gap electronic states associated with the IDB defects. STS measurements also reveal energy bandgaps of monolayer (ML) and bilayer (BL) MoSe2. ML WSe2 thin films were also grown at varying conditions on HOPG substrates through the Van der Waals epitaxy process and the growth characteristics were found similar to that of MoSe2. However, differences are also noted, particularly about the IDB defects. Contrary to MoSe2, as-grown WSe2 films do not contain the line defects. The reason behind such differences will be discussed. Finally, besides the STM/S studies about the morphological and electronic properties of MBE MoSe2 and WSe2 films, high quality samples have been synthesized on graphene-on-SiC substrate with reduced defect density and well-controlled thicknesses for some ex situ characterizations by photoluminescence and Raman spectroscopy methods. The results will be summarized and discussed in this thesis. Subjects: Molecular beam epitaxy Metallic films
Book Synopsis Investigation of Two-Dimensional Transition Metal Dichalcogenides with Time-of-Flight Secondary Ion Mass Spectrometry by : Rita Tilmann
Download or read book Investigation of Two-Dimensional Transition Metal Dichalcogenides with Time-of-Flight Secondary Ion Mass Spectrometry written by Rita Tilmann and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis 2D Metal Carbides and Nitrides (MXenes) by : Babak Anasori
Download or read book 2D Metal Carbides and Nitrides (MXenes) written by Babak Anasori and published by Springer Nature. This book was released on 2019-10-30 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the rapidly expanding field of two-dimensional (2D) transition metal carbides and nitrides (MXenes). It covers fundamental knowledge on synthesis, structure, and properties of these new materials, and a description of their processing, scale-up and emerging applications. The ways in which the quickly expanding family of MXenes can outperform other novel nanomaterials in a variety of applications, spanning from energy storage and conversion to electronics; from water science to transportation; and in defense and medical applications, are discussed in detail.
Download or read book 2D Materials written by Phaedon Avouris and published by Cambridge University Press. This book was released on 2017-06-29 with total page 521 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn about the most recent advances in 2D materials with this comprehensive and accessible text. Providing all the necessary materials science and physics background, leading experts discuss the fundamental properties of a wide range of 2D materials, and their potential applications in electronic, optoelectronic and photonic devices. Several important classes of materials are covered, from more established ones such as graphene, hexagonal boron nitride, and transition metal dichalcogenides, to new and emerging materials such as black phosphorus, silicene, and germanene. Readers will gain an in-depth understanding of the electronic structure and optical, thermal, mechanical, vibrational, spin and plasmonic properties of each material, as well as the different techniques that can be used for their synthesis. Presenting a unified perspective on 2D materials, this is an excellent resource for graduate students, researchers and practitioners working in nanotechnology, nanoelectronics, nanophotonics, condensed matter physics, and chemistry.
Book Synopsis 2D Semiconductor Materials and Devices by : Dongzhi Chi
Download or read book 2D Semiconductor Materials and Devices written by Dongzhi Chi and published by Elsevier. This book was released on 2019-10-19 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2D Semiconductor Materials and Devices reviews the basic science and state-of-art technology of 2D semiconductor materials and devices. Chapters discuss the basic structure and properties of 2D semiconductor materials, including both elemental (silicene, phosphorene) and compound semiconductors (transition metal dichalcogenide), the current growth and characterization methods of these 2D materials, state-of-the-art devices, and current and potential applications. Reviews a broad range of emerging 2D electronic materials beyond graphene, including silicene, phosphorene and compound semiconductors Provides an in-depth review of material properties, growth and characterization aspects—topics that could enable applications Features contributions from the leading experts in the field
Book Synopsis Introduction to Scanning Tunneling Microscopy by : C. Julian Chen
Download or read book Introduction to Scanning Tunneling Microscopy written by C. Julian Chen and published by . This book was released on 2008 with total page 423 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scanning tunneling and the atomic force microscope, both capable of imaging individual atoms, were crowned with the Physics Nobel Prize in 1986, and are the cornerstones of nanotechnology today. This is a thoroughly updated version of this 'bible' in the field.
Book Synopsis Investigating and Tuning the Properties of 2-dimensional Materials Via Doping, Strain, and Optical Techniques by : Amber McCreary
Download or read book Investigating and Tuning the Properties of 2-dimensional Materials Via Doping, Strain, and Optical Techniques written by Amber McCreary and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of graphene in 2004, there has been a significant amount of research dedicated to van der Waals solids, which have strong in-plane coupling and weak interlayer interactions that allows their thickness to be reduced down to few or even single layers. Along with graphene, transition metal dichalcogenides (TMDs) such as MoS2, WS2, and ReS2 are among these van der Waals solids and display remarkable properties. The research contained within this dissertation investigates the optical properties of these 2-Dimensional (2D) materials as well as utilizes substitutional doping and strain to tune their properties. Chapter 1 discusses the structure, properties, growth, and characterization of various 2D materials. In Chapter 2, the synthesis of high quality boron-doped graphene is demonstrated using atmospheric-pressure chemical vapor deposition (CVD) that was characterized by Raman, scanning tunneling microscopy, and X-ray photoelectron spectroscopy. It was also shown to have unique sensing capabilities for detecting toxic gases such as NH3 and NO2 in extremely low concentrations (i.e. parts per billion/parts per trillion). In Chapter 3, the Raman and photoluminescence (PL) of single, bi, and few-layered MoS2 grown by powder vaporization as a function of strain is studied through the development of a method to apply uniaxial strain to the material while collecting Raman and PL. Before this study, there were no reports on how the properties of few-layered MoS2 under strain were influenced by the number of layers, even though it has been shown that the transport properties of few-layers are more favorable than their monolayered counterparts. Chapter 4 addresses the significant variation in transport and optical properties found in the literature on TMDs by studying the Raman and PL of monolayered WS2 produced via different growth methods. Distinct features that indicate the degree of crystallinity in WS2 were observed and it was determined that PL is drastically more sensitive to the quality of the material than Raman spectroscopy. Finally, the optical properties of a relatively new TMD, ReS2, are investigated in Chapter 5. Due to the distorted crystal structure of ReS2, its optical and electrical properties are highly anisotropic. A detailed polarization-dependent study was performed for all of the 18 first order Raman modes for different number of layers. In addition, through a resonant Raman study, it was demonstrated that there are striking and unexpected signatures in the Raman spectrum illuminated with different laser wavelengths that need to be considered when using Raman spectroscopy to characterize the orientation of ReS2 and other anisotropic materials.
