Download or read book Two dimensional Coherent Spectroscopy of Monolayer Transition Metal Dichalcogenides written by Chandriker Kavir Dass and published by . This book was released on 2015 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional semiconductors have long been studied for their unique optical and electronic properties, but with the work of Novoselov and Geim on van der Waals materials, two-dimensional semiconductors have seen a surge of renewed interest. This dissertation focuses on monolayer transition metal dichalcogenides (TMDCs), a class of two-dimensional materials that can easily be fabricated by mechanical exfoliation, much like graphene. In their bulk form, these materials have indirect band gaps, but transition to direct gap semiconductors in the monolayer limit. The band-edge optical response of TMDCs, like WSe2 and MoS2, is dominated by exciton absorption occurring at the ±K-points of the Brillouin zone. Because of the unique electronic structure of these materials, these two points form distinct valleys in the band structure which can be exploited to produce valley polarization. Exciton quantum dynamics are characterized by two fundamental parameters, one of which is the dephasing rate, [gamma], which describes quantum dissipation arising from the interaction of the excitons with their environment (i.e. other excitons, impurities, etc...). This dissertation focuses on measuring the fundamental property of dephasing time (which is inversely proportional to the dephasing rate and homogeneous linewidth) in monolayer WSe2 through the use of two-dimensional coherent spectroscopy. Our measurements have revealed a homogeneous linewidth consistent with dephasing times in the sub-picosecond regime. We also characterize the role of exciton-exciton and exciton-phonon interactions, on the homogeneous linewidth, through excitation density and temperature dependent studies. These studies have revealed strong many-body effects and nonradiative population relaxation as the primary dephasing mechanisms. Microscopic calculations show that in perfect crystalline samples of monolayer TMDCs, the radiative lifetimes are also in the sub-picosecond regime due to the large oscillator strengths inherent in these materials. This result is consistent with the short dephasing times found experimentally.
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 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 Optical Multidimensional Coherent Spectroscopy written by Associate Professor Hebin Li and published by Oxford University Press. This book was released on 2023-02-28 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an introduction to optical multidimensional coherent spectroscopy, a relatively new method of studying materials based on using ultrashort light pulses to perform spectroscopy. The technique has been developed and perfected over the last 25 years, resulting in multiple experimental approaches and applications to a broad array of systems ranging from atoms and molecules to solids and biological systems. Indeed, while this method is most often used by physical chemists, it is also relevant to materials of interest to physicists, which is the primary focus of this book. As well as an introduction to the method, the book also provides tutorials on the interpretation of the rather complex spectra that is broadly applicable across all subfields, and finishes with a survey of several emerging material systems and a discussion of future directions.
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 Encyclopedia of Modern Optics written by Bob D. Guenther and published by Academic Press. This book was released on 2018-02-14 with total page 2253 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Encyclopedia of Modern Optics, Second Edition, Five Volume Set provides a wide-ranging overview of the field, comprising authoritative reference articles for undergraduate and postgraduate students and those researching outside their area of expertise. Topics covered include classical and quantum optics, lasers, optical fibers and optical fiber systems, optical materials and light-emitting diodes (LEDs). Articles cover all subfields of optical physics and engineering, such as electro-optical design of modulators and detectors. This update contains contributions from international experts who discuss topics such as nano-photonics and plasmonics, optical interconnects, photonic crystals and 2D materials, such as graphene or holy fibers. Other topics of note include solar energy, high efficiency LED’s and their use in illumination, orbital angular momentum, quantum optics and information, metamaterials and transformation optics, high power fiber and UV fiber lasers, random lasers and bio-imaging. Addresses recent developments in the field and integrates concepts from fundamental physics with applications for manufacturing and engineering/design Provides a broad and interdisciplinary coverage of specialist areas Ensures that the material is appropriate for new researchers and those working in a new sub-field, as well as those in industry Thematically arranged and alphabetically indexed, with cross-references added to facilitate ease-of-use
Download or read book Semiconductor Optics 2 written by Heinz Kalt and published by Springer Nature. This book was released on with total page 567 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 Quantum Coherent Dynamics of Excitons and Valley Pseudospins in Atomically Thin Semiconductors written by Kai Hao (Ph. D.) and published by . This book was released on 2018 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Monolayer transition metal dichalcogenides (TMDCs) are new emerging van der Waals materials. Several TMDC materials go through with a transition from indirect to direct gap semiconductors when reduced to monolayer thickness limit with emission in the visible to near-infrared range, making them attractive materials for optoelectronic applications. Their near-gap optical properties are dominant by excitons (bound electron-hole pairs), charged excitons (known as trions) or higher order bound states (e.g., neutral and charged biexcitons). In this dissertation, we explored the quantum coherent dynamics of exciton, trions and their associated valley index using a powerful ultrafast spectroscopy tool known as the two-dimensional coherent spectroscopy (2DCS). We investigated the underlying mechanisms that determined the valley coherence associated with excitons and trions. In monolayer TMDCs, there are two inequivalent K and K' points in momentum space, where the band extrema are located and the excitons are formed. The excitonic states in the two valleys are selectively coupled to light with opposite helicity. This valley contrasting optical selection rules allow one to address and manipulate the valley index readily, a unique property and advantage of TMDC materials for valleytronic applications. The valley coherence can be quantitatively evaluated in polarization resolved zero-quantum 2D spectra. We found that the exciton valley coherence is limited by the electron-hole exchange interaction in the system. In contrast, for the charged exciton (trion) states, where the inter-valley scattering is suppressed, it is the intra-valley pure dephasing limits the inter-valley coherence time. These results provide the insight of valley coherence dynamics in monolayer TMDCs and suggest possible approaches to improve the valley coherence time. Next, we investigate the coherence coupling between excitons and trions created in one valley. The trions are charged quasiparticles which contribute to the charge transport directly. Thus, the coupling between exciton and trion states can significantly influent the interpretation of transport measurements. We demonstrate that these two types of quasiparticles are coherently coupled to each other by the observation of the quantum beating of the cross-diagonal peaks in one-quantum 2D spectra. The coherence time between them can be extracted by monitoring the amplitude decay of the beating signal. We found that the coherent coupling dephasing rate between the exciton and trion equals to the sum of the exciton and trion dephasing rate, indicating uncorrelated dephasing process for excitons and trions. At longer time scale, the phonon-assisted energy transfer couples the two states incoherently. Finally, we studied the higher order correlated states in monolayer TMDCs. We used polarization resolved 2DCS to reveal bounded inter-valley neutral biexcitons and charged biexcitons as new peaks which spectrally shifted in 2D spectra. The binding energies of these biexcitons are ∼20 and ∼5 meV respectively. Unlike linear optical spectroscopy studies, the 2D spectra separate the different quantum pathways. Hence, these spectra provide unambiguous evidence of the biexciton states. The extracted binding energy of the biexciton states agrees with theoretical calculation and resolves controversies in the literature. Biexciton formation is important for applications such as lasers and generations of entangled photon pairs.
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 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.
Download or read book Duality Symmetry written by Ivan Fernandez-Corbaton and published by MDPI. This book was released on 2020-12-10 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Symmetry is one of the most general concepts in physics. Symmetry arguments are used to explain and predict observations at all length scales, from elementary particles to cosmology. The generality of symmetry arguments, combined with their simplicity, makes them a powerful tool for both fundamental and applied investigations. In electrodynamics, one of the symmetries is the invariance of the equations under exchange of electric and magnetic quantities. The continuous version of this symmetry is most commonly known as electromagnetic duality symmetry. This concept has been accepted for more than a century, and, throughout this time, has influenced other areas of physics, like high energy physics and gravitation. This Special Issue is devoted to electromagnetic duality symmetry and other vareities of dualities in physics. It contains four Articles, one Review and one Perspective. The context of the contributions ranges from string theory to applied nanophotonics, which, as anticipated, shows that duality symmetries in general and electromagnetic duality symmetry in particular are useful in a wide variety of physics fields, both theoretical and applied. Moreover, a number of the contributions show how the use of symmetry arguments and the quantification of symmetry breaking can successfully guide our theoretical understanding and provide us with guidelines for system design.
Download or read book Beyond CMOS written by Alessandro Cresti and published by John Wiley & Sons. This book was released on 2023-07-19 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in physics, material sciences and technology have allowed the rise of new paradigms with bright prospects for digital electronics, going beyond the reach of Moore's law, which details the scaling limit of electronic devices in terms of size and power. This book presents original and innovative topics in the field of beyond CMOS electronics, ranging from steep slope devices and molecular electronics to spintronics, valleytronics, superconductivity and optical chips. Written by globally recognized leading research experts, each chapter of this book will provide an introductory overview of their topic and illustrate the state of the art and future challenges. Aimed not only at students and those new to this field, but also at well-experienced researchers, Beyond-CMOS provides extremely clear and exciting perspectives about the technology of tomorrow, and is thus an effective tool for understanding and developing new ideas, materials and architectures.
Download or read book MODIFICATION OF TRANSITION METAL DICHALCOGENIDES OPTICAL ELECTRICAL AND MAGNETIC PROPERTIES THROUGH ALLOYING written by Mingzu Liu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on two-dimensional (2D) transition metal dichalcogenides (TMDs), and studies the modification of their physical properties through the method of substitutional doping/alloying. The controlled synthesis and novel properties such as room-temperature ferromagnetism in doped/alloyed 2D TMD systems are investigated. Two notes are addressed here: 1) The general concept of TMDs contains a large family of binary compounds, while we are mainly concentrated on the semiconducting members (sTMDs) inside, including MoS2, WS2, MoSe2, and WSe2. 2) The term of alloying is applied here to denote the situation where impurity atoms are incorporated intentionally into the host 2D lattice, with a concentration greater than 1 at%, while conventionally, the term of doping is only adapted to describe similar cases but with significantly lower concentrations less than 1 at%, and even less than 1000 ppm = 0.1 at% in some literatures. However, a clear quantitative classification between the two concepts does not exist, and we will study cases with a wide range of impurity concentrations in this dissertation. Therefore, we will indiscriminately use both the terms of doping and alloying for convenience, regardless of the exact concentration/amount of impurity atoms. The main context of this dissertation is outlined as follows. In Chapter 1, we will introduce the fundamentals of 2D TMD materials and techniques for 2D surface characterizations. 2D magnetism is one of the most active fields in condensed matter physics, and will be a major topic of our research, thus a brief introduction in principles of magnetic materials will also be given. Controllable substitutional doping/alloying in monolayer 2D materials is a prerequisite to any further characterizations and applications. In Chapter 2, we will first introduce the liquid-phase precursor-assisted chemical vapor deposition (CVD) method we developed for universal substitutional doping with tunable dopant concentrations in sTMDs. Different dopant elements are successfully incoporated in sTMD monolayers, and the defect types and optical properties are studied. It is then discovered that the edge termination in single crystal sTMD monolayers will greatly affect the spatial distribution of dopant atoms, and this effect is elucidated through the synthesis of doped hexagonal sTMD monolayers that have as-grown domains with different dopant concentrations. Combined with the solution-based CVD method we developed, the edge termination can be utilized for engineering in-plane heterojunctions that display fascinating electronic, optoelectronic, and magnetic properties. Long-range ferromagnetic ordering has been considered as hard to achieve for a long time in 2D systems, especially at room temperature. In Chapter 3, we will demonstrate room-temperature ferromagnetism in vanadium-doped (V-doped) sTMD monolayers and its coupling with the thermal, optical, and electrical properties. The magnetization is dependent on both the dopant concentration and temperature, and an abnormal crossover in the hysteresis loop of monolayer V-WSe2 is described, which is attributed to a strong 2D thermally induced spin flip phenomenon. The ferromagnetism is induced by indirect exchange interactions between V moments, which are mediated by hole carriers. It is then revealed that optical excitations creating excess hole carriers can be used to control the magnetization. Finally, we attempt on applying the induced magnetization to break the degeneracy in the valley degrees of freedom through a circularly polarized photoluminescence (PL) experiment, and look into the effect of magnetization on the optical emissions. The 2D magnetic systems based on V-doped sTMD monolayers hold great promise for novel magneto-electronic or magneto-optical devices, as well as offering a platform for fundamental physical studies. Magnetic domain structure is an inherent phenomenon in finite-size ferromagnetic systems. In Chapter 4, we will discuss the direct visulization of magnetic domains in Vdoped sTMD monolayers. Magnetic force microscopy (MFM) is first used in the tentative observation of domain structures experimentally, and a mathematical model is proposed to estimate the signal level. Lorentz transmission electron microscopy (Lorentz-TEM) is then used, and the observation of an field-dependent reversible domain contrast is reported in monolayer V-WS2. The contrast signal is revealed to be highly affected by the sample magnetization orientation and charge doping, which are mainly determined by the dopant concentration, beam-sample interactions and the type of substrates. Atomic-resolution electron microscopy is finally performed to detect potential connections between lattice atomic motions and macroscopic magnetization. The observed contrast signals on V-doped sTMD provide primary knowledge in domain structures of 2D diluted magnetic systems, and is the first reported imaging of a monolayer magnetic material through Lorentz-TEM. Finally, Chapter 5 summarizes the studies discussed in this dissertation, and provides outlooks to potential continuing future works.
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 Semiconductor Optics and Transport Phenomena written by Wilfried Schäfer and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: Well-balanced and up-to-date introduction to the field of semiconductor optics, including transport phenomena in semiconductors. Starting with the theoretical fundamentals of this field the book develops, assuming a basic knowledge of solid-state physics. The application areas of the theory covered include semiconductor lasers, detectors, electro-optic modulators, single-electron transistors, microcavities and double-barrier resonant tunneling diodes. One hundred problems with hints for solution help the readers to deepen their knowledge.
Download or read book Quantum Dot Photodetectors written by Xin Tong and published by Springer Nature. This book was released on 2021-09-17 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of state-of-the-art quantum dot photodetectors, including device fabrication technologies, optical engineering/manipulation strategies, and emerging photodetectors with building blocks of novel quantum dots (e.g. perovskite) as well as their hybrid structured (e.g. 0D/2D) materials. Semiconductor quantum dots have attracted much attention due to their unique quantum confinement effect, which allows for the facile tuning of optical properties that are promising for next-generation optoelectronic applications. Among these remarkable properties are large absorption coefficient, high photosensitivity, and tunable optical spectrum from ultraviolet/visible to infrared region, all of which are very attractive and favorable for photodetection applications. The book covers both fundamental and frontier research in order to stimulate readers' interests in developing novel ideas for semiconductor photodetectors at the center of future developments in materials science, nanofabrication technology and device commercialization. The book provides a knowledge sharing platform and can be used as a reference for researchers working in the fields of photonics, materials science, and nanodevices.
