Excitons in Transition Metal Dichalcogenide Van Waals Heterostructures PDF Download

Author: Erica Calman
Publisher:
ISBN:
Category :
Languages : en
Pages : 53

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Book Description
Excitons are quasi-partciles consisting of an electro-statically bound electron and hole which have long been observed in semiconducting and insulating materials. A spatially indirect exciton (IX) is an exciton in which the electron and the hole are spatially separated. This is achieved through the use of a static electric field and engineered semiconductor heterosteructures. Indirect excitons interact with one another and can effeciently re-radiate, so they provide a means for light to interact with light in solid media, and can thus be used for ecient optical signal processing. However, the most common material for studying indirect excitons (GaAs) cannot support excitons at temperatures above ~ 100 K. This limitation, due to hermal fluctuations having enough energy to cause exciton dissocation prevents the creation of practical devices for excitonic signal processing. This dissertation demonstrates an increase in the binding energy and thus operating temperature of indirect excitons by utelizing van der Waals transition metal dichalcogenide heterostructures. These atomically thin materials have binding energies on the order of 0:5 eV which support excitons at 300 K.

Author: Phaedon Avouris
Publisher: Cambridge University Press
ISBN: 1316738132
Category : Technology & Engineering
Languages : en
Pages : 521

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Book Description
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.

Author: Junho Choi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Van der Waals (vdW) heterostructures represent a promising material platform with rich electronic and optical properties highly tunable via a wide selection of layer materials, electric doping, strain, and twist angle. Monolayers of transition metal dichalcogenide (TMD) semiconductors commonly show strong light-matter coupling and direct bandgaps from the infrared to the visible spectral range, making them promising candidates for various optoelectronic applications. Vertically stacking different TMD monolayers allows one to create TMD heterostructures with rich and tunable correlated electronic phases and optical properties. Among different methods to tune the properties of vdW heterostructures, the twist angle is the most unique parameter. In this dissertation, we investigated the twist angle dependent optical properties of interlayer excitons in TMD heterostructures. First, we studied the twist-angle dependent interlayer exciton lifetimes in MoSe2/WSe2 heterostructures. We found that the multiple resonances of interlayer excitons subject to strong confinement in the moiré potential. Their properties are consistent with the interpretation that these resonances are ground- and excited state excitons. Our experiments further revealed that the recombination dynamics of interlayer excitons depends strongly on the twist angle. For example, their lifetimes change from ~ 1 ns to hundreds of ns when the twist angle is increased from 1 to 3.5°. In collaboration with a theoretical group, we explored two mechanisms for this drastic dependence. First, a relative rotation between the two layers in real space translates to a rotation in the momentum space. As the twist angle is increased, the interlayer exciton transitions change from direct- to indirect transitions in the momentum spacing, leading to a longer lifetime. Second, the presence of moiré potential also has a significant impact on the lifetime, reducing its angle dependence by relaxing the requirement of momentum conservation. Next, we investigated the influence of moiré potential on interlayer exciton diffusion in MoSe2/WSe2 heterostructures. The interlayer exciton diffusion offers a unique channel of energy and information transport in TMD heterostructures. While early studies focused on how mobile excitons are in TMD heterostructures, we find that interlayer exciton diffusion is impeded in the presence of the moiré potential by comparing two types of samples: those prepared by mechanical exfoliation and those grown with chemical vapor deposition. We investigated multiple mechanically stacked samples with accurately controlled twist-angles. We showed that the interlayer exciton diffusion does not depend on the size of the moiré supercell in a simple and monotonic manner. These experiments provide an important and complementary view of the diffusion properties of interlayer excitons from those reported in the literature

Author: Hartmut Haug
Publisher: World Scientific
ISBN: 9789810218645
Category : Science
Languages : en
Pages : 496

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Book Description
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.

Author: Zheng Zhang
Publisher: John Wiley & Sons
ISBN: 3527349502
Category : Technology & Engineering
Languages : en
Pages : 340

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Book Description
Van der Waals Heterostructures A comprehensive resource systematically detailing the developments and applications of van der Waals heterostructures and devices Van der Waals Heterostructures is essential reading to understand the developments made in van der Waals heterostructures and devices in all aspects, from basic synthesis to physical analysis and heterostructures assembling to devices applications, including demonstrated applications of van der Waals heterostructure on electronics, optoelectronics, and energy conversion, such as solar energy, hydrogen energy, batteries, catalysts, biotechnology, and more. This book starts from an in-depth introduction of van der Waals interactions in layered materials and the forming of mixed-dimensional heterostructures via van der Waals force. It then comprehensively summarizes the synthetic methods, devices building processes and physical mechanism of 2D van der Waals heterostructures, and devices including 2D-2D electronics, 2D-2D optoelectronics, and mixed dimensional van der Waals heterostructures. In Van der Waals Heterostructures, readers can expect to find specific information on: The current library of 2D semiconductors and the current synthesis and performances of 2D semiconductors Controllable synthesis and assemble van der Waals heterostructures, physics of the van der Waals interface, and multi-field coupling effects 2D-2D electronics, 2D-2D optoelectronics, mixed dimensional van der Waals heterostructures, and van der Waals heterostructure applications on energy conversion Insight into future perspectives of the van der Waals heterostructures and devices with the detailed effective role of 2D materials for integrated electrical and electronic equipment

Author: Alexander V. Kolobov
Publisher: Springer
ISBN: 3319314505
Category : Technology & Engineering
Languages : en
Pages : 545

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Book Description
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.

Author: Lewis H. Fowler-Gerace
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Spatially indirect excitons (IXs), also known as interlayer excitons, are bound pairs of an electron and a hole in spatially separated layers. IXs can propagate over long distances before they recombine into light, and they can cool down below the temperature of quantum degeneracy within their lifetimes, which can be controlled by gate voltage up to microseconds and beyond. These properties make IXs a promising platform for studying fundamental physics phenomena and as the medium for highly efficient signal processing devices. IXs were originally studied in gallium arsenide (GaAs) heterostructures, where IXs have shown evidence for Bose-Einstein condensation, and proof of principle has been demonstrated for excitonic transistors and excitonic integrated circuits. IXs only exist at low temperatures in GaAs systems due to the low IX binding energy on the order of 10 meV. In the transition-metal dichalcogenide (TMD) heterostructure system, the IX binding energy is predicted to be more than two orders of magnitude higher, making IXs stable at room temperature and allowing for the possibility of high temperature IX superfluidity. To date, observation of some of the key IX behaviors, namely the long-range IX transport and evidence of IX condensation, has remained elusive in the TMD system. This dissertation characterizes the IX spectrum in a MoSe2/WSe2 heterostructure, demonstrates the realization and control of long-range IX propagation using a new mechanism beyond the know mechanism for IX control in GaAs heterostructures, and separately identifies a quantum origin for the propagation of IXs generated by resonant excitation in the TMD heterostructure.

Author: Narayanasamy Sabari Arul
Publisher: Springer
ISBN: 9811390452
Category : Technology & Engineering
Languages : en
Pages : 361

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Book Description
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.

Author: Ivan Pelant
Publisher: OUP Oxford
ISBN: 019162750X
Category : Science
Languages : en
Pages : 557

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Book Description
This book reviews up-to-date ideas of how the luminescence radiation in semiconductors originates and how to analyze it experimentally. The book fills a gap between general textbooks on optical properties of solids and specialized monographs on luminescence. It is unique in its coherent treatment of the phenomenon of luminescence from the very introductory definitions, from light emission in bulk crystalline and amorphous materials to the advanced chapters that deal with semiconductor nano objects, including spectroscopy of individual nanocrystals. The theory of radiative recombination channels in semiconductors is considered on a level of intuitive physical understanding rather than rigorous quantum mechanical treatment. The book is based on teaching and written in the style of a graduate text with plenty of tutorial material, illustrations, and problem sets at chapter ends. It is designed predominantly for students in physics, optics, optoelectronics and materials science.

Author: Zongyu Huang
Publisher: CRC Press
ISBN: 1000562840
Category : Science
Languages : en
Pages : 166

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Book Description
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.