Download or read book Coherent Light Matter Interactions in Monolayer Transition Metal Dichalcogenides written by Edbert Jarvis Sie and published by Springer. This book was released on 2017-11-11 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents optical methods to split the energy levels of electronic valleys in transition-metal dichalcogenides (TMDs) by means of coherent light-matter interactions. The electronic valleys found in monolayer TMDs such as MoS2, WS2, and WSe2 are among the many novel properties exhibited by semiconductors when thinned down to a few atomic layers, and have have been proposed as a new way to carry information in next generation devices (so-called valleytronics). These valleys are, however, normally locked in the same energy level, which limits their potential use for applications. The author describes experiments performed with a pump-probe technique using transient absorption spectroscopy on MoS2 and WS2. It is demonstrated that hybridizing the electronic valleys with light allows one to optically tune their energy levels in a controllable valley-selective manner. In particular, by using off-resonance circularly polarized light at small detuning, one can tune the energy level of one valley through the optical Stark effect. Also presented within are observations, at larger detuning, of a separate contribution from the so-called Bloch--Siegert effect, a delicate phenomenon that has eluded direct observation in solids. The two effects obey opposite selection rules, enabling one to separate the two effects at two different valleys.

Download or read book A Study of Metal Interactions with Transition Metal Dichalcogenides written by Ama Duffie Agyapong and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As field effect transistors (FETs) continue to shrink towards the sub-nanometer regime, interest in two-dimensional transition metal dichalcogenides (2D TMDs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS¬2) grows. Unlike three-dimensional semiconductors, many 2D TMDs remain semiconducting at sub-nanometer thicknesses, which is favorable for the electrostatics of scaled devices. Critical to the successful integration of TMDs in FETs is reducing contact resistance at the metal/semiconductor interface and understanding how metal contacts form on the TMD van der Waals surface. Beyond electronics, there are other fields in which the interactions of metals on TMDs are important, such as catalysis. The goal of this dissertation is to better understand metal/TMD interfaces by examining interfacial reactions, epitaxy of ordered and disordered intermetallic alloys, and the impact of different metal deposition conditions on the structure and doping of TMD monolayers. The first study aims to investigate the reactivity between contact metals (Ti, Al, Cu, Pd, and Au) and 1L WS2. Studies of this buried interface often require destructive techniques, such as using a focused ion beam to access the buried metal/TMD interface for microscopy, which is time-consuming and could potentially modify the interface. The goal of this study was to non-destructively detect interfacial reactions at this interface using Raman spectroscopy as a screening tool to distinguish reactive metals quickly and effectively from non-reactive metals. Our approach involved acquiring Raman spectra from the backside of the metal/WS2 stack through a single-crystal transparent sapphire growth substrate, which allowed us to probe the interface between a coalesced metal film and 1L WS2. The disappearance of the Raman-active phonon modes for WS2 suggested the consumption of WS2 through reactions with the continuous metal film, as observed completely for Ti upon deposition and nearly completely for Al after annealing at and above 100 °C. On the other hand, the persistence of multiple Raman-active phonon modes for WS2 confirms that Au, Cu, and Pd are unreactive with WS2 upon deposition and after cumulatively annealing for 1 h at 100, 200, and 300 °C, even though unreactive metal overlayers could shift some of the peaks in the spectrum. Results matched thermodynamic predictions of metals on bulk WS2. A subsequent study focused on applying criteria for room- and low-temperature quasi-van der Waals epitaxy for elements on MoS2 and WSe2 to the synthesis of highly-oriented single-crystal intermetallic phases on MoS2 growth templates. In addition to thermodynamic stability between the film and substrate, we also considered crystallographic symmetry and atomic mobilities in our selection of intermetallic catalysts to synthesize (PdIn, PdCu, PtAl2, PtCu, PtBi, and PtSn). The phases were directly cosputtered onto exfoliated MoS2 on TEM grids by DC magnetron sputtering with the exception of PtBi where the Pt layer was sputtered, and the Bi layer was evaporated by electron beam evaporation. The Bi/Pt layers were then annealed on a hotplate at 200 °C for 60 min in an ambient environment. We collected plan-view transmission electron microscopy (TEM) images and selected-area electron diffraction (SAED) patterns to determine the phase, crystallinity, and orientation of the intermetallics on MoS2. The resulting PdIn film was highly oriented or textured for as-deposited and annealed conditions with an orientation relationship of PdIn(111)∥MoS_2 (0001); PdIn[11 ̅0]∥MoS_2 [11 ̅00]. We were able to form epitaxial PdCu film at room temperature and after annealing, although they were disordered, obtaining the orientational relationship PdCu(111)∥MoS_2 (0001); PdCu[2 ̅11]∥MoS_2 [11 ̅00]. PtCu was epitaxial at room temperature and after annealing; however, it formed a disordered phase on MoS2 at room temperature with the orientation relationship of PtCu(111)∥MoS_2 (0001);PtCu[2 ̅11]∥MoS_2 [11 ̅00] and an ordered phase on MoS2 after annealing with the orientation relationship of PtCu(0001)∥MoS_2 (0001);PtCu[11 ̅00]∥MoS_2 [11 ̅00]. We observed regions of annealed PtAl2 films in which the (100) PtAl2 plane aligned with the basal plane of MoS2. However, we were unsuccessful in depositing epitaxial PtSn and PtBi on MoS2, possibly due to reaction between S-Sn and incomplete intermixing, respectively. In the final part of this dissertation, we examined the effects of physical vapor deposition of contact metals on 1L MoS2 using the non-destructive backside-illumination Raman spectroscopy method. Metal films (Cu, Pd, Pt, Bi, Sn, and In) were deposited via electron beam (e-beam) evaporation and DC magnetron sputtering at a nominal thickness of 100 nm, except for evaporated Pt (70 nm), which was made thinner due to heat generated during its evaporation. We were able to observe the persistence of the characteristic MoS2 first-order Raman modes after the evaporation of all metals; however, some sputtered metals (Pd, Pt, Sn, and In) showed evidence of damaged 1L MoS2, which resulted in the disappearance of the MoS2 phonon vibrational modes. The degree of damage induced by the sputtering process could be related to the kinetic energies of the atomic species as they arrive at the MoS2 surface. We were able to correlate the disappearance of the first-order Raman modes of the MoS2 beneath the sputtered metals with the cohesive energies of the metals, which correlates with experimentally measured impinging forces of sputtered species from the literature. Our results also indicated that metals with higher cohesive and adsorption energies were more likely to damage monolayer TMDs during sputter deposition. In some cases, we observed the first-order out-of-plane MoS2 vibrational mode redshift or else become two distinct peaks, which tells us about electron doping of MoS2 by metals with modest cohesive and adsorption energies (Bi, In, Sn, and Au). The appearance of the two peaks seems to be linked to metal clusters forming during thin-film deposition and/or bilayer regions on monolayer MoS2, which may result in inhomogeneous doping. The studies presented in this dissertation expand our fundamental understanding of 3D metallic films on 2D semiconductors. They demonstrate and apply a powerful screening tool that provides a non-destructive approach to observing changes at the buried metal/TMD interface. They furthermore contribute to our understanding of the growth of metal and alloy films prepared by physical vapor deposition on transition metal dichalcogenides.

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.

Download or read book Magnetic Interactions in Transition Metal Dichalcogenides written by Oscar Rodrigo Avalos Ovando and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Metal metal Interactions in Some Novel Covalently Linked Transition Metal Complexes written by Manawadevi Y. Udugala-Ganehenege and published by . This book was released on 2000 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

Download or read book Theory of Exciton exciton Interactions in Monolayer Transition Metal Dichalcogenides written by Florian Manuel Katsch and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies in the Structural Chemistry of Transition Metal Complexes with Agostic and Metal hydrogen Interactions written by Stephen Anthony Litster and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrons at the Fermi Surface written by Springford and published by Cambridge University Press. This book was released on 2011-03-03 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: First published in 1980, this is a Festschrift to honour Professor David Schoenberg, FRS, on the subject of electrons at the Fermi surface.

Download or read book On Being Well coordinated A Half century Of Research On Transition Metal Complexes written by John L Burmeister and published by World Scientific. This book was released on 2003-10-14 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt: This invaluable book distils the research accomplishments of Professor Fred Basolo during the five decades when he served as a world leader in the modern renaissance of inorganic chemistry. Its primary focus is on the very important area of chemistry known as coordination chemistry.Most of the elements in the periodic table are metals, and most of the chemistry of metals involves coordination chemistry. This is the case in the currently significant areas of research, including organometallic homogenous catalysis, biological reactions of metalloproteins, and even the solid state extended structures of new materials. In these systems, the metals are of primary importance because they are the sites of ligand substitution or redox reactions. In the solid materials, the coordination number of the metal and its stereochemistry are of major importance.Some fifty years of research on transition metal complexes carried out in the laboratory of Professor Basolo at Northwestern University is recorded here as selected scientific publications. The book is divided into three different major research areas, each dealing with some aspect of coordination chemistry. In each case, introductory remarks are presented which indicate what prompted the research projects and what the major accomplishments were. Although the research was of the academic, curiosity-driven type, some aspects have proven to be useful to others involved in projects that were much more applied in nature.

Download or read book Transition Metal and Rare Earth Compounds written by Hartmut Yersin and published by Springer. This book was released on 2014-03-12 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies of the interactions of small coadsorbed molecules on transition metal surfaces written by Diane Elaine Ewing Peebles and published by . This book was released on 1983 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Carbon Nanotubes written by M. Endo and published by Elsevier. This book was released on 2013-10-22 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes have been studied extensively in relation to fullerenes, and together with fullerenes have opened a new science and technology field on nano scale materials.A whole range of issues from the preparation, structure, properties and observation of quantum effects in carbon nanotubes in comparison with 0-D fullerenes are discussed.In addition, complementary reviews on carbon nanoparticles such as carbon nano-capsules, onion-like graphite particles and metal-coated fullerenes are covered.This book aims to cover recent research and development in this area, and so provide a convenient reference tool for all researchers in this field. It is also hoped that this book can serve to stimulate future work on carbon nanotubes.

Download or read book Transition Metal and Rare Earth Compounds written by Hartmut Yersin and published by Springer Science & Business Media. This book was released on 2001-01-11 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal and rare earth compounds are investigated intensively because of important questions concerning fundamental research problems. More recently also their enormous potential for the development of new materials for photophysical and photochemical applications has been explored. Thus, it is important to focus on a deeper understanding of the elctronic energies, transition prohabilities, intermolecular interactions, etc.. This task has been accomplished by leading researchers in the field. They present introductions into, but also detailed reviews of the current state of knowledge of three different subjects.

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

Download or read book Extended Interactions Between Metal Ions in Transition Metal Complexes written by and published by . This book was released on 1974 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: