Download or read book Probing Excitonic Mechanics in Suspended and Strained Transition Metal Dichalcogenides Monolayers written by Hongchao Xie and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decade, the interest in two-dimensional (2D) materials, especially for atomically thin transition metal dichalcogenide (TMD) semiconductors, had dramatically thrived for both fundamental science and practical applications. The reduced dielectric screening in 2D mainly attributes to the strong excitonic effect in atomically thin TMD semiconductors. This pronounced exciton feature can maintain at room temperature, which indicates strong light-matter interaction and possible optoelectronic application using monolayer semiconductors. Meanwhile, the absence of inversion symmetry and out-of-plane mirror symmetry jointly endows carriers in monolayer TMDs with a new valley degree of freedom (DOF). Namely, in hexagonally-arranged lattice of 2D materials, electrons that residing at band edges of K and K valleys can carry opposite valley magnetic moments and Berry curvatures, which allows the further control of valley-indexed carriers with polarized light, electrical and magnetic fields. Besides, the large strain sustainability of monolayer TMDs gives rise to mechanically tunable band gap with 70 meV redshift per 1% strain up to recorded 10% applied strain. Thus, the interaction of macroscopic mechanical means with valley electrons makes monolayer TMD semiconductor a promising platform to implement novel valley-controlled mechanical devices. This motivates the experimental studies demonstrated in this dissertation.In this dissertation, we investigate the valley contrasting coupling between optoelectronic carriers (exciton & flowing electrons) and mechanics in a monolayer TMD semiconductor. In the first parts (Chapter 1&2), I will present emerging properties of TMD monolayers and discuss interesting physics that can study after suspending or straining these atomically thin materials. The fabrication and measurement of typical TMD suspended devices will also be demonstrated in details. In the secondary part (Chapter 3), we demonstrate robust exciton bistability by continuous-wave optical excitation in a suspended monolayer WSe2 at a much lower intensity level of 103 W/cm2. The observed bistability is originated from a photothermal mechanism, which can provide both optical nonlinearity and internal passive feedback in a simple cavity-less structure. This is supported by detailed excitation wavelength and power dependence studies of the sample reflectance, as well as by numerical simulation including the temperature-dependent optical response of monolayer WSe2. Furthermore, under a finite magnetic field, the bistability becomes valley dependent and controllable not only by light intensity but also by light helicity due to the exciton valley Zeeman effect, which open up an exciting opportunity in controlling light with light using monolayer materials.In the following part (Chapter 4), we report the observation of exciton-optomechanical coupling in a suspended monolayer MoSe2 mechanical resonator. In particular, we have observed light-induced damping and anti-damping of mechanical vibrations and modulation of the mechanical spring constant by moderate optical pumping near the exciton resonance with variable detuning. The observed exciton-optomechanical coupling strength is also highly gate-tunable. Our observations can be fully explained by a model based on photothermal backaction and gate-induced mirror symmetry breaking in the device structure. The observation of gate-tunable exciton-optomechanical coupling in a monolayer semiconductor may find novel applications in nanoelectromechanical systems (NEMS) and in exciton-optomechanics.In the last part of this dissertation (Chapter 5), we present the study of magnetization purely originated from the valley DOF in strained MoS2 monolayers. By breaking the three-fold rotational symmetry in single-layer MoS2 via a uniaxial stress, we have demonstrated the pure electrical generation of valley magnetization in this material, and its direct imaging by Kerr rotation microscopy. The observed out-of-plane magnetization is independent of in-plane magnetic field, linearly proportional to the in-plane current density, and optimized when the current is orthogonal to the strain-induced piezoelectric field. These results are fully consistent with a theoretical model of valley magnetoelectricity driven by Berry curvature effects. Furthermore, the effect persists at room temperature, opening possibilities for practical valleytronic devices.
Download or read book Probing Transition Metal Dichalcogenide Monolayers and Heterostructures by Optical Spectroscopy 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: We then compare our results with the exciton lifetime in MoS2/WS2 and MoSe2/WSe2 heterostructures. In TMDC/TMDC heterostructures, the decrease in exciton lifetime is twice that in WS2/graphene heterostructures and due predominantly to charge transfer between the layers. Finally, we probe the band alignment in MoS2/WS2 heterostructures using scanning tunneling microscopy (STM) and spectroscopy (STS).We confirm the monolayer band gaps and the predicted type II band alignment in the heterostructure. Drawing from all the research presented, we arrive at a favorable conclusion about the viability of TMDC based devices.
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 Trion Formation Dynamics in Monolayer Transition Metal Dichalcogenides written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we report charged exciton (trion) formation dynamics in doped monolayer transition metal dichalcogenides, specifically molybdenum diselenide (MoSe2), using resonant two-color pump-probe spectroscopy. When resonantly pumping the exciton transition, trions are generated on a picosecond time scale through exciton-electron interaction. As the pump energy is tuned from the high energy to low energy side of the inhomogeneously broadened exciton resonance, the trion formation time increases by ~50%. This feature can be explained by the existence of both localized and delocalized excitons in a disordered potential and suggests the existence of an exciton mobility edge in transition metal dichalcogenides.
Download or read book Valley Dynamics and Excitonic Properties in Monolayer Transition Metal Dichalcogenides written by Louis Bouet and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The possibility of isolating transition metal dichalcogenide monolayers by simple experimental means has been demonstrated in 2005, by the same technique used for graphene. This has sparked extremely diverse and active research by material scientists, physicists and chemists on these perfectly two-dimensional (2D) materials. Their physical properties inmonolayer formare appealing both fromthe point of view of fundamental science and for potential applications. Transition metal dichalcogenidemonolayers such asMoS2 have a direct optical bandgap in the visible and show strong absorption of the order of 10% per monolayer. For transistors based on single atomic layers, the presence of a gap allows to obtain high on/off ratios.In addition to potential applications in electronics and opto-electronics these 2D materials allow manipulating a new degree of freedom of electrons, in addition to the spin and the charge : Inversion symmetry breaking in addition to the strong spin-orbit coupling result in very original optical selection rules. The direct bandgap is situated at two non-equivalent valleys in k-space, K+ and K-. Using a specific laser polarization, carriers can be initialized either in the K+ or K- valley, allowing manipulating the valley index of the electronic states. This opens up an emerging research field termed "valleytronics". The present manuscript contains a set of experiments allowing understanding and characterizing the optoelectronic properties of these new materials. The first chapter is dedicated to the presentation of the scientific context. The original optical and electronic properties of monolayer transition metal dichalcogenides are demonstrated using a simple theoreticalmodel. The second chapter presents details of the samples and the experimental setup. Chapters 3 to 6 present details of the experiments carried out and the results obtained. We verify experimentally the optical selection rules. We identify the different emission peaks in the monolayer materials MoS2, WSe2 and MoSe2. In time resolved photoluminescence measurements we study the dynamics of photo-generated carriersand their polarization. An important part of this study is dedicated to experimental investigations of the properties of excitons, Coulomb bound electron-hole pairs. In the final experimental chapter, magneto-Photoluminescence allows us to probe the electronic band structure and to lift the valley degeneracy.
Download or read book Quantum Confined Excitons in 2 Dimensional Materials written by Carmen Palacios-Berraquero and published by Springer. This book was released on 2018-11-02 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the first established experimental results of an emergent field: 2-dimensional materials as platforms for quantum technologies, specifically through the optics of quantum-confined excitons. It also provides an extensive review of the literature from a number of disciplines that informed the research, and introduces the materials of focus – 2d Transition Metal Dichalcogenides (2d-TMDs) – in detail, discussing electronic and chemical structure, excitonic behaviour and response to strain. This is followed by a brief overview of quantum information technologies, including concepts such as single-photon sources and quantum networks. The methods chapter addresses quantum optics techniques and 2d-material processing, while the results section shows the development of a method to deterministically create quantum dots (QDs) in the 2d-TMDs, which can trap single-excitons; the fabrication of atomically thin quantum light-emitting diodes to induce all-electrical single-photon emission from the QDs, and lastly, the use of devices to controllably trap single-spins in the QDs –the first step towards their use as optically-addressable matter qubits.
Download or read book Advances in Condensed Matter and Materials Physics written by Jagannathan Thirumalai and published by BoD – Books on Demand. This book was released on 2020-05-06 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, Condensed Matter and Material Physics, incorporates the work of multiple authors to enhance the theoretical as well as experimental knowledge of materials. The investigation of crystalline solids is a growing need in the electronics industry. Micro and nano transistors require an in-depth understanding of semiconductors of different groups. Amorphous materials, on the other hand, as non-equilibrium materials are widely applied in sensors and other medical and industrial applications. Superconducting magnets, composite materials, lasers, and many more applications are integral parts of our daily lives. Superfluids, liquid crystals, and polymers are undergoing active research throughout the world. Hence profound information on the nature and application of various materials is in demand. This book bestows on the reader a deep knowledge of physics behind the concepts, perspectives, characteristic properties, and prospects. The book was constructed using 10 contributions from experts in diversified fields of condensed matter and material physics and its technology from over 15 research institutes across the globe.
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.
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 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
Download or read book Silicon Nanocrystals written by Lorenzo Pavesi and published by John Wiley & Sons. This book was released on 2010-02-02 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique collection of knowledge represents a comprehensive treatment of the fundamental and practical consequences of size reduction in silicon crystals. This clearly structured reference introduces readers to the optical, electrical and thermal properties of silicon nanocrystals that arise from their greatly reduced dimensions. It covers their synthesis and characterization from both chemical and physical viewpoints, including ion implantation, colloidal synthesis and vapor deposition methods. A major part of the text is devoted to applications in microelectronics as well as photonics and nanobiotechnology, making this of great interest to the high-tech industry.
Download or read book MoS2 written by Zhiming M. Wang and published by Springer Science & Business Media. This book was released on 2013-11-18 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the structure and electronic, magnetic, and other properties of various MoS2 (Molybdenum disulfide) nanostructures, with coverage of synthesis, Valley polarization, spin physics, and other topics. MoS2 is an important, graphene-like layered nano-material that substantially extends the range of possible nanostructures and devices for nanofabrication. These materials have been widely researched in recent years, and have become an attractive topic for applications such as catalytic materials and devices based on field-effect transistors (FETs) and semiconductors. Chapters from leading scientists worldwide create a bridge between MoS2 nanomaterials and fundamental physics in order to stimulate readers' interest in the potential of these novel materials for device applications. Since MoS2 nanostructures are expected to be increasingly important for future developments in energy and other electronic device applications, this book can be recommended for Physics and Materials Science and Engineering departments and as reference for researchers in the field.
Download or read book Quantum Theory of the Optical and Electronic Properties of Semiconductors written by Hartmut Haug and published by World Scientific. This book was released on 1994 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook presents the basic elements needed to understand and engage in research in semiconductor physics. It deals with elementary excitations in bulk and low-dimensional semiconductors, including quantum wells, quantum wires and quantum dots. The basic principles underlying optical nonlinearities are developed, including excitonic and many-body plasma effects. The fundamentals of optical bistability, semiconductor lasers, femtosecond excitation, optical Stark effect, semiconductor photon echo, magneto-optic effects, as well as bulk and quantum-confined Franz-Keldysh effects are covered. The material is presented in sufficient detail for graduate students and researchers who have a general background in quantum mechanics.
Download or read book Advanced Biosensors for Health Care Applications written by Raju Khan and published by Elsevier. This book was released on 2019-06-15 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Biosensors for Health Care Applications highlights the different types of prognostic and diagnostic biomarkers associated with cancer, diabetes, Alzheimer's disease, brain and retinal diseases, cardiovascular diseases, bacterial infections, as well as various types of electrochemical biosensor techniques used for early detection of the potential biomarkers of these diseases. Many advanced nanomaterials have attracted intense interests with their unique optical and electrical properties, high stability, and good biocompatibility. Based on these properties, advanced nanoparticles have been used as biomolecular carriers, signal producers, and signal amplifiers in biosensor design. Recent studies reported that there are several diagnostic methods available, but the major issue is the sensitivity and selectivity of these approaches. This book outlines the need of novel strategies for developing new systems to retrieve health information of patients in real time. It explores the potential of nano-multidisciplinary science in the design and development of smart sensing technology using micro-nanoelectrodes, novel sensing materials, integration with MEMS, miniaturized transduction systems, novel sensing strategy, that is, FET, CMOS, System-on-a-Chip (SoC), Diagnostic-on-a-Chip (DoC), and Lab-on-a-Chip (LOC), for diagnostics and personalized health-care monitoring. It is a useful handbook for specialists in biotechnology and biochemical engineering. - Describes advanced nanomaterials for biosensor applications - Relates the properties of available nanomaterials to specific biomarkers applications - Includes diagnosis and electrochemical studies based on biosensors - Explores the potential of nano-multidisciplinary science to design and develop smart sensing technologies - Describes novel strategies for developing a new class of assay systems to retrieve the desired health information
Download or read book 2D Monoelemental Materials Xenes and Related Technologies written by Zongyu Huang and published by CRC Press. This book was released on 2022-04-19 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Monoelemental 2D materials called Xenes have a graphene-like structure, intra-layer covalent bond, and weak van der Waals forces between layers. Materials composed of different groups of elements have different structures and rich properties, making Xenes materials a potential candidate for the next generation of 2D materials. 2D Monoelemental Materials (Xenes) and Related Technologies: Beyond Graphene describes the structure, properties, and applications of Xenes by classification and section. The first section covers the structure and classification of single-element 2D materials, according to the different main groups of monoelemental materials of different components and includes the properties and applications with detailed description. The second section discusses the structure, properties, and applications of advanced 2D Xenes materials, which are composed of heterogeneous structures, produced by defects, and regulated by the field. Features include: Systematically detailed single element materials according to the main groups of the constituent elements Classification of the most effective and widely studied 2D Xenes materials Expounding upon changes in properties and improvements in applications by different regulation mechanisms Discussion of the significance of 2D single-element materials where structural characteristics are closely combined with different preparation methods and the relevant theoretical properties complement each other with practical applications Aimed at researchers and advanced students in materials science and engineering, this book offers a broad view of current knowledge in the emerging and promising field of 2D monoelemental materials.
Download or read book Quantum Dot Devices written by Zhiming M. Wang and published by Springer Science & Business Media. This book was released on 2012-05-24 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum dots as nanomaterials have been extensively investigated in the past several decades from growth to characterization to applications. As the basis of future developments in the field, this book collects a series of state-of-the-art chapters on the current status of quantum dot devices and how these devices take advantage of quantum features. Written by 56 leading experts from 14 countries, the chapters cover numerous quantum dot applications, including lasers, LEDs, detectors, amplifiers, switches, transistors, and solar cells. Quantum Dot Devices is appropriate for researchers of all levels of experience with an interest in epitaxial and/or colloidal quantum dots. It provides the beginner with the necessary overview of this exciting field and those more experienced with a comprehensive reference source.
Download or read book Semiconductor Nanostructures written by Dieter Bimberg and published by Springer Science & Business Media. This book was released on 2008-06-03 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reducing the size of a coherently grown semiconductor cluster in all three directions of space to a value below the de Broglie wavelength of a charge carrier leads to complete quantization of the energy levels, density of states, etc. Such “quantum dots” are more similar to giant atoms in a dielectric cage than to classical solids or semiconductors showing a dispersion of energy as a function of wavevector. Their electronic and optical properties depend strongly on their size and shape, i.e. on their geometry. By designing the geometry by controlling the growth of QDs, absolutely novel possibilities for material design leading to novel devices are opened. This multiauthor book written by world-wide recognized leaders of their particular fields and edited by the recipient of the Max-Born Award and Medal 2006 Professor Dieter Bimberg reports on the state of the art of the growing of quantum dots, the theory of self-organised growth, the theory of electronic and excitonic states, optical properties and transport in a variety of materials. It covers the subject from the early work beginning of the 1990s up to 2006. The topics addressed in the book are the focus of research in all leading semiconductor and optoelectronic device laboratories of the world.
