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Author: Jonghwan Kim Publisher: ISBN: Category : Languages : en Pages : 71
Book Description
Recently, atomically thin 2D materials have emerged as a new class of nanomaterial with extraordinary physical properties ranging from semi-metal (graphene), semiconductors (transition metal dichalcogenides) to insulators (hBN). Due to its unusual linear electronic spectrum, graphene has been studied as a platform where exotic quantum mechanical phenomena take place and electro-optical property can be greatly tuned by electrostatic gating. On the other hand, in semiconducting transition metal dichalcogenides (TMD), many body particles such as exciton and trion can be readily accessed even at room temperature due to strong Coulomb interaction. There are further exciting opportunities in heterostructures where layer-layer interaction provides new physics and functionalities. In this thesis, I explore light-matter interaction in 2D materials and their heterostructure with laser spectroscopy techniques. First of all, I study electromagnetic interaction between graphene and optical cavity via Rayleigh scattering spectroscopy. Although light-matter interaction in graphene is extremely strong for atomically thin thickness, overall optical response in macroscopic scale is still limited. Combination of graphene and resonant cavity can amplify the interaction dramatically. Therefore, it is important to understand the electromagnetic interaction between two systems. In this study, I find that the coupling can be explained by real and imaginary part of graphene dielectric constant which affects cavity resonance frequency and quality factor, respectively. In addition to fundamental interest, it also shows that this platform has promising potential for novel sensing application and electro-optical modulator. Secondly, I study valley-selective dipole interaction of exciton states in a monolayer transition metal dichalcogenides. Due to crystal symmetry, an extra degree of freedom, valley state, is available in this system. In analogy to spin state, it is important to understand and manipulate valley state with light. In this study, I demonstrate that valley excitonic states in a monolayer WSe2 can be manipulated by femtosecond pulse with the control of polarization. Ultrafast pump-probe spectroscopy shows that circularly-polarized femtosecond pulse induces valley-selective optical Stark effect which acts as a pseudomagnetic field. This demonstrates efficient and ultrafast control of the valley excitons with optical light, and opens up the possibility to coherent manipulate the valley polarization for quantum information applications. Lastly, I study interlayer interaction in heterostructure of MoS2/WS2 where strong exciton binding energy plays an important role. Simple band theory predicts that a heterostructure of two different semiconducting TMD layers forms type-II heterostructure. However, it is not clear how strong Coulomb interaction plays a role in terms of charge transfer dynamics. In this study, I demonstrate ultrafast charge transfer in MoS2/WS2 via both photoluminescence mapping and femtosecond (fs) pump-probe spectroscopy. Despite large exciton binding energy, hole transfer from the MoS2 layer to the WS2 layer takes place within 50 fs after optical excitation. Such ultrafast charge transfer in van der Waals heterostructures indicates that it can enable novel 2D devices for optoelectronics and light harvesting.
Author: Jonghwan Kim Publisher: ISBN: Category : Languages : en Pages : 71
Book Description
Recently, atomically thin 2D materials have emerged as a new class of nanomaterial with extraordinary physical properties ranging from semi-metal (graphene), semiconductors (transition metal dichalcogenides) to insulators (hBN). Due to its unusual linear electronic spectrum, graphene has been studied as a platform where exotic quantum mechanical phenomena take place and electro-optical property can be greatly tuned by electrostatic gating. On the other hand, in semiconducting transition metal dichalcogenides (TMD), many body particles such as exciton and trion can be readily accessed even at room temperature due to strong Coulomb interaction. There are further exciting opportunities in heterostructures where layer-layer interaction provides new physics and functionalities. In this thesis, I explore light-matter interaction in 2D materials and their heterostructure with laser spectroscopy techniques. First of all, I study electromagnetic interaction between graphene and optical cavity via Rayleigh scattering spectroscopy. Although light-matter interaction in graphene is extremely strong for atomically thin thickness, overall optical response in macroscopic scale is still limited. Combination of graphene and resonant cavity can amplify the interaction dramatically. Therefore, it is important to understand the electromagnetic interaction between two systems. In this study, I find that the coupling can be explained by real and imaginary part of graphene dielectric constant which affects cavity resonance frequency and quality factor, respectively. In addition to fundamental interest, it also shows that this platform has promising potential for novel sensing application and electro-optical modulator. Secondly, I study valley-selective dipole interaction of exciton states in a monolayer transition metal dichalcogenides. Due to crystal symmetry, an extra degree of freedom, valley state, is available in this system. In analogy to spin state, it is important to understand and manipulate valley state with light. In this study, I demonstrate that valley excitonic states in a monolayer WSe2 can be manipulated by femtosecond pulse with the control of polarization. Ultrafast pump-probe spectroscopy shows that circularly-polarized femtosecond pulse induces valley-selective optical Stark effect which acts as a pseudomagnetic field. This demonstrates efficient and ultrafast control of the valley excitons with optical light, and opens up the possibility to coherent manipulate the valley polarization for quantum information applications. Lastly, I study interlayer interaction in heterostructure of MoS2/WS2 where strong exciton binding energy plays an important role. Simple band theory predicts that a heterostructure of two different semiconducting TMD layers forms type-II heterostructure. However, it is not clear how strong Coulomb interaction plays a role in terms of charge transfer dynamics. In this study, I demonstrate ultrafast charge transfer in MoS2/WS2 via both photoluminescence mapping and femtosecond (fs) pump-probe spectroscopy. Despite large exciton binding energy, hole transfer from the MoS2 layer to the WS2 layer takes place within 50 fs after optical excitation. Such ultrafast charge transfer in van der Waals heterostructures indicates that it can enable novel 2D devices for optoelectronics and light harvesting.
Author: Yilei Li Publisher: Springer ISBN: 331925376X Category : Science Languages : en Pages : 80
Book Description
This thesis focuses on the study of the optical response of new atomically thin two-dimensional crystals, principally the family of transition metal dichalcogenides like MoS2. One central theme of the thesis is the precise treatment of the linear and second-order nonlinear optical susceptibilities of atomically thin transition metal dichalcogenides. In addition to their significant scientific interest as fundamental material responses, these studies provide essential knowledge and convenient characterization tools for the application of these 2D materials in opto-electronic devices. Another important theme of the thesis is the valley physics of atomically thin transition metal dichalcogenides. It is shown that the degeneracy in the valley degree of freedom can be lifted and a valley polarization can be created using a magnetic field, which breaks time reversal symmetry in these materials. These findings enhance our basic understanding of the valley electronic states and open up new opportunities for valleytronic applications using two-dimensional materials.
Author: Kyle Lee Seyler Publisher: ISBN: Category : Languages : en Pages :
Book Description
Layered materials are excellent systems for investigating physics in two dimensions. Understanding the optical response of 2D layered materials and their heterostructures at the atomically thin limit is an important aspect of this field. Photoexcitations, such as excitons, critically impact future optoelectronic technologies, such as next-generation solar cells, light-emitting diodes, lasers, and single-photon sources. Moreover, they can provide deep insights into the rich electronic properties of the host crystals, especially in two dimensions, where stronger electron confinement, symmetry changes, and interfacial effects are often very influential. The 2D semiconducting transition metal dichalcogenides, for example, have garnered tremendous excitement for their strong light-matter interactions, which involve tightly bound excitons with intriguing spin-valley physics. Furthermore, newly discovered 2D magnets are unlocking new opportunities to explore magnetic photoexcitations in the atomically thin limit. This dissertation presents optical spectroscopy experiments that probe the fundamental photoexcitations within 2D semiconducting transition metal dichalcogenides, magnetic chromium triiodide (CrI3), and their van der Waals heterostructures. First, we show how second-harmonic generation spectroscopy serves as a powerful probe of excitons and trions in monolayer WSe2 and demonstrate an electrical exciton-based second-harmonic generation switch. We then add MoSe2 to the picture, forming MoSe2/WSe2 heterobilayers in which we reveal the valley-contrasting physics of long-lived free and trapped interlayer excitons. Next, we introduce atomically thin CrI3 and describe our observation of spontaneous circularly polarized photoluminescence. We also unravel its ligand-field and charge-transfer-dominated photoresponse, which broadens the landscape of 2D material photoexcitations beyond excitons. Finally, we combine ultrathin layers of CrI3 with monolayer WSe2, where we discover unprecedented control of valley excitons in monolayer WSe2 by magnetic proximity to CrI3.
Author: Paulo André Dias Gonçalves Publisher: Springer Nature ISBN: 3030382915 Category : Science Languages : en Pages : 232
Book Description
This thesis presents a comprehensive theoretical description of classical and quantum aspects of plasmonics in three and two dimensions, and also in transdimensional systems containing elements with different dimensionalities. It focuses on the theoretical understanding of the salient features of plasmons in nanosystems as well as on the multifaceted aspects of plasmon-enhanced light–matter interactions at the nanometer scale. Special emphasis is given to the modeling of nonclassical behavior across the transition regime bridging the classical and the quantum domains. The research presented in this dissertation provides useful tools for understanding surface plasmons in various two- and three-dimensional nanostructures, as well as quantum mechanical effects in their response and their joint impact on light–matter interactions at the extreme nanoscale. These contributions constitute novel and solid advancements in the research field of plasmonics and nanophotonics that will help guide future experimental investigations in the blossoming field of nanophotonics, and also facilitate the design of the next generation of truly nanoscale nanophotonic devices.
Author: Qiang Wang Publisher: John Wiley & Sons ISBN: 3527350594 Category : Technology & Engineering Languages : en Pages : 373
Book Description
Comprehensive resource covering concepts, perspectives, and skills required to understand the preparation, nonlinear optics, and applications of two-dimensional (2D) materials Bringing together many interdisciplinary experts in the field of 2D materials with their applications in nonlinear optics, Two-Dimensional Materials for Nonlinear Optics covers preparation methods for various novel 2D materials, such as transition metal dichalcogenides (TMDs) and single elemental 2D materials, excited-state dynamics of 2D materials behind their outstanding performance in photonic devices, instrumentation for exploring the photoinduced excited-state dynamics of the 2D materials spanning a wide time scale from ultrafast to slow, and future trends of 2D materials on a series of issues like fabrications, dynamic investigations, and photonic/optoelectronic applications. Powerful nonlinear optical characterization techniques, such as Z-scan measurement, femtosecond transient absorption spectroscopy, and microscopy are also introduced. Edited by two highly qualified academics with extensive experience in the field, Two-Dimensional Materials for Nonlinear Optics covers sample topics such as: Foundational knowledge on nonlinear optical properties, and fundamentals and preparation methods of 2D materials with nonlinear optical properties Modulation and enhancement of optical nonlinearity in 2D materials, and nonlinear optical characterization techniques for 2D materials and their applications in a specific field Novel nonlinear optical imaging systems, ultrafast time-resolved spectroscopy for investigating carrier dynamics in emerging 2D materials, and transient terahertz spectroscopy 2D materials for optical limiting, saturable absorber, second and third harmonic generation, nanolasers, and space use With collective insight from researchers in many different interdisciplinary fields, Two-Dimensional Materials for Nonlinear Optics is an essential resource for materials scientists, solid state chemists and physicists, photochemists, and professionals in the semiconductor industry who are interested in understanding the state of the art in the field.
Author: Yoke Khin Yap Publisher: MDPI ISBN: 3038424927 Category : Technology & Engineering Languages : en Pages : 153
Book Description
This book is a printed edition of the Special Issue "Two-Dimensional Electronics and Optoelectronics" that was published in Electronics
Author: Dongzhi Chi Publisher: Elsevier ISBN: 0128165898 Category : Technology & Engineering Languages : en Pages : 338
Book Description
2D Semiconductor Materials and Devices reviews the basic science and state-of-art technology of 2D semiconductor materials and devices. Chapters discuss the basic structure and properties of 2D semiconductor materials, including both elemental (silicene, phosphorene) and compound semiconductors (transition metal dichalcogenide), the current growth and characterization methods of these 2D materials, state-of-the-art devices, and current and potential applications. Reviews a broad range of emerging 2D electronic materials beyond graphene, including silicene, phosphorene and compound semiconductors Provides an in-depth review of material properties, growth and characterization aspects—topics that could enable applications Features contributions from the leading experts in the field
Author: Rafik Addou Publisher: Elsevier ISBN: 032390310X Category : Technology & Engineering Languages : en Pages : 434
Book Description
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
Author: Stefan Alexander Maier Publisher: Springer Science & Business Media ISBN: 0387378251 Category : Technology & Engineering Languages : en Pages : 234
Book Description
Considered a major field of photonics, plasmonics offers the potential to confine and guide light below the diffraction limit and promises a new generation of highly miniaturized photonic devices. This book combines a comprehensive introduction with an extensive overview of the current state of the art. Coverage includes plasmon waveguides, cavities for field-enhancement, nonlinear processes and the emerging field of active plasmonics studying interactions of surface plasmons with active media.
Author: Yuerui Lu Publisher: CRC Press ISBN: 0429767994 Category : Science Languages : en Pages : 189
Book Description
Two-dimensional (2D) materials have attracted tremendous interest since the study of graphene in the early 21st century. With their thickness in the angstrom-to-nanometer range, 2D materials, including graphene, transition metal dichalcogenides, phosphorene, silicene, and other inorganic and organic materials, can be an ideal platform to study fundamental many-body interactions because of reduced screening and can also be further engineered for nanophotonic applications. This book compiles research outcomes of leading groups in the field of 2D materials for nanophotonic physics and devices. It describes research advances of 2D materials for various nanophotonic applications, including ultrafast lasers, atomically thin optical lenses, and gratings to inelastically manipulate light propagation, their integrations with photonic nanostructures, and light–matter interactions. The book focuses on actual applications, while digging into the physics underneath. It targets advanced undergraduate- and graduate-level students of nanotechnology and researchers in nanotechnology, physics, and chemistry, especially those with an interest in 2D materials.