Free Charge Carrier Properties In Group Iii Nitrides And Graphene Studied By Thz To Mir Ellipsometry And Optical Hall Effect
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Free Charge Carrier Properties In Group Iii Nitrides And Graphene Studied By Thz To Mir Ellipsometry And Optical Hall Effect
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Author : Nerijus Armakavicius
language : en
Publisher: Linköping University Electronic Press
Release Date : 2019-03-05
Free Charge Carrier Properties In Group Iii Nitrides And Graphene Studied By Thz To Mir Ellipsometry And Optical Hall Effect written by Nerijus Armakavicius and has been published by Linköping University Electronic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-03-05 with categories.
Development of silicon based electronics have revolutionized our every day life during the last five decades. Nowadays silicon based devices operate close to their theoretical limits that is becoming a bottleneck for further progress. In particular, for the growing field of high frequency and high power electronics, silicon cannot offer the required properties. Development of materials capable of providing high current densities, carrier mobilities and high breakdown fields is crucial for further progress in state of the art electronics. Epitaxial graphene grown on semi-insulating silicon carbide substrates has a high potential to be integrated in current planar device technologies. High electron mobilities and sheet carrier densities make graphene extremely attractive for high frequency analog applications. One of the remaining challenges is the interaction of epitaxial graphene with the substrate. Typically, much lower free charge carrier mobilities, compared to free standing graphene, and doping, due to charge transfer from the substrate, is reported. Thus, a good understanding of the intrinsic free charge carriers properties and the factors affecting them is very important for further development of epitaxial graphene. Group III-nitrides have been extensively studied and already have proven their high efficiency as light emitting diodes for short wavelengths. High carrier mobilities and breakdown electric fields were demonstrated for group III-nitrides, making them attractive for high frequency and high power applications. Currently, In-rich InGaN alloys and AlGaN/GaN high electron mobility structures are of high interest for the research community due to open fundamental questions such as free charge carrier properties at high temperatures and wavefunction hybridization in AlGaN/GaN heterostructures. Electrical characterization techniques, commonly used for the determination of free charge carrier properties, require good ohmic and Schottky contacts, which in certain cases can be difficult to achieve. Access to electrical properties of buried conductive channels in multilayered structures requires modification of samples and good knowledge of the electrical properties of all electrical junctions within the structure. Moreover, the use of contacts to electrically characterize two-dimensional electronic materials, such as graphene, can alter their intrinsic properties. Furthermore, the determination of effective mass parameters commonly employs cyclotron resonance and Shubnikov-de Haas oscillations measurements, which require long scattering times of free charge carriers, high magnetic fields and low temperatures. The optical Hall effect is an external magnetic-field induced birefringence of conductive layers due to the free charge carriers interaction with long-wavelength electromagnetic waves under the influence of the Lorentz force. The optical Hall effect can be measured by generalized ellipsometry and provides a powerful method for the determination of free charge carrier properties in a non-destructive and contactless manner. The optical Hall effect measurements can provide quantitative information about free charge carrier type, concentration, mobility and effective mass parameters at temperatures ranging from few kelvins to room temperature and above. It further allows to differentiate the free charge carrier properties of individual layers in multilayer samples. The employment of a backside cavity for transparent samples can enhance the optical Hall effect and allows to access free charge carrier properties at relatively low magnetic fields using permanent magnet. The optical Hall effect measurements at mid-infrared spectral range can be used to probe quantum mechanical phenomena such as Landau levels in graphene. The magnetic field dependence of the inter-Landau level transition energies and optical polarization selection rules provide information about coupling properties between graphene layers and the electronic band structure. Measurement of the optical Hall effect by generalized ellipsometry is an indirect technique requiring subsequent data analysis. Parameterized optical models are fitted to match experimentally measured ellipsometric spectra by varying physically significant model parameters. Analysis of the generalized ellipsometry data at long wavelengths for samples containing free charge carriers by optical models based on the classical Drude formulation, augmented with an external magnetic field contribution, allows to extract carrier concentration, mobility and effective mass parameters. The development of the integrated FIR and THz frequency-domain ellipsometer at the Terahertz Materials Analysis Center in Linköping University was part of the graduate studies presented in this dissertation. The THz ellipsometer capabilities are demonstrated by determination of Si and sapphire optical constants, and free charge carrier properties of two-dimensional electron gas in GaN-based high electron mobility transistor structures. The THz ellipsometry is further shown to be capable of determining free charge carrier properties and following their changes upon variation of ambient conditions in atomically thin layers with an example of epitaxial graphene. A potential of the THz OHE with the cavity enhancement (THz-CE-OHE) for determination of the free charge carrier properties in atomically thin layers were demonstrated by the measurements of the carrier properties in monolayer and multilayer epitaxial graphene on Si-face 4H-SiC. The data analysis revealed p-type doping for monolayer graphene with a carrier density in the low 1012 cm-2 range and a carrier mobility of 1550 cm2V-1s-1. For the multilayer graphene, n-type doping with a carrier density in the low 1013 cm-2 range, a mobility of 470 cm2V-1s-1 and an effective mass of (0.14 ± 0.03)m0 were extracted. Different type of doping among monolayer and multilayer graphene is explained as a result of different hydrophobicity among samples. Further, we have employed THz-CE-OHE to determine for the first time anisotropic mobility parameter in quasi-free-standing bilayer epitaxial graphene induced by step-like surface morphology of 4H-SiC. Correlation of atomic force microscopy, Raman scattering spectroscopy, scanning probe Kelvin probe microscopy, low energy electron microscopy and diffraction analysis allows us to investigate the possible scattering mechanisms and suggests that anisotropic mobility is induced by varying local mobility parameter due to interaction between graphene and underlaying substrate. The origin of the layers decoupling in multilayer graphene on C-face 4H-SiC was studied by MIR-OHE, transmission electron microscopy and electron energy loss spectroscopy. The results revealed the decoupling of the layers induced by the increased interlayer spacing which is attributed to the Si atoms trapped between graphene layers. MIR ellipsometry and MIR-OHE measurements were employed to determine the electron effective mass in a wurtzite In0.33Ga0.67N epitaxial layer. The data analysis revealed the effective mass parameters parallel and perpendicular to the c-axis which can be considered as equal within sensitivity of our measurements. The determined effective mass is consistent with linear dependence on the In content. Analysis of the free charge carrier properties in AlGaN/GaN high electron mobility structures with modified interfaces showed that AlGaN/GaN interface structure has a significant effect on the mobility parameter. A sample with a sharp interface layers exhibits a record mobility of 2332 ± 73 cm2V-1s-1. The determined effective mass parameters showed an increase compared to the bulk GaN value, which is attributed to the penetration of the electron wavefunction into the AlGaN barrier layer. Temperature dependence of free charge carrier properties in GaN-based high electron mobility transistor structures with AlGaN and InAlN barrier layers were measured by terahertz optical Hall effect technique in a temperature range from 7.2 K to 398 K. The results revealed strong changes in the effective mass and mobility parameters. At temperatures below 57 K very high carrier mobility parameters above 20000 cm2V-1s-1 for AlGaN-barrier sample and much lower mobilities of ~ 5000 cm2V-1s-1 for InAlN-barrier sample were obtained. At low temperatures the effective mass parameters for both samples are very similar to bulk GaN value, while at temperatures above 131 K effective mass shows a strong increase with temperature. The effective masses of 0.344 m0 (@370 K) and 0.439 m0 (@398 K) were obtained for AlGaN- and InAlN-barrier samples, respectively. We discussed the possible origins of effective mass enhancement in high electron mobility transistor structures.
Study Of Novel Electronic Materials By Mid Infrared And Terahertz Optical Hall Effect
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Author : Nerijus Armakavicius
language : en
Publisher: Linköping University Electronic Press
Release Date : 2017-10-23
Study Of Novel Electronic Materials By Mid Infrared And Terahertz Optical Hall Effect written by Nerijus Armakavicius and has been published by Linköping University Electronic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-10-23 with categories.
Development of silicon based electronics have revolutionized our every day life during the last three decades. Nowadays Si based devices operate close to their theoretical limits that is becoming a bottleneck for further progress. In particular, for the growing field of high frequency and high power electronics, Si cannot offer the required properties. Development of materials capable of providing high current densities, carrier mobilities and high breakdown fields is crucial for a progress in state of the art electronics. Epitaxial graphene grown on semi-insulating silicon carbide substrates has a high potential to be integrated in the current planar device technologies. High electron mobilities and sheet carrier densities make graphene extremely attractive for high frequency analog applications. One of the remaining challenges is the interaction of epitaxial graphene with the substrate. Typically, much lower free charge carrier mobilities, compared to free standing graphene, and doping, due to charge transfer from the substrate, is reported. Thus, a good understanding of the intrinsic free charge carriers properties and the factors affecting them is very important for further development of epitaxial graphene. III-group nitrides have been extensively studied and already have proven their high efficiency as light sources for short wavelengths. High carrier mobilities and breakdown electric fields were demonstrated for III-group nitrides, making them attractive for high frequency and high power applications. Currently, In-rich InGaN alloys and AlGaN/GaN high electron mobility structures are of high interest for the research community due to open fundamental questions. Electrical characterization techniques, commonly used for the determination of free charge carrier properties, require good ohmic and Schottky contacts, which in certain cases can be difficult to achieve. Access to electrical properties of buried conductive channels in multilayered structures requires modification of samples and good knowledge of the electrical properties of all electrical contact within the structure. Moreover, the use of electrical contacts to electrically characterize two-dimensional electronic materials, such as graphene, can alter their intrinsic properties. Furthermore, the determination of effective mass parameters commonly employs cyclotron resonance and Shubnikov-de Haas oscillations measurements, which require long scattering times of free charge carriers, high magnetic fields and low temperatures. The optical Hall effect is an external magnetic field induced optical anisotropy in conductive layers due to the motion of the free charge carriers under the influence of the Lorentz force, and is equivalent to the electrical Hall effect at optical frequencies. The optical Hall effect can be measured by generalized ellipsometry and provides a powerful method for the determination of free charge carrier properties in a non-destructive and contactless manner. In principle, a single optical Hall effect measurement can provide quantitative information about free charge carrier types, concentrations, mobilities and effective mass parameters at temperatures ranging from few kelvins to room temperature and above. Further, it was demonstrated that for transparent samples, a backside cavity can be employed to enhance the optical Hall effect. Measurement of the optical Hall effect by generalized ellipsometry is an indirect technique requiring subsequent data analysis. Parameterized optical models are fitted to match experimentally measured ellipsometric data by varying physically significant parameters. Analysis of the optical response of samples, containing free charge carriers, employing optical models based on the classical Drude model, which is augmented with an external magnetic field contribution, provide access to the free charge carrier properties. The main research results of the graduate studies presented in this licentiate thesis are summarized in the five scientific papers. Paper I. Description of the custom-built terahertz frequency-domain spectroscopic ellipsometer at Linköping University. The terahertz ellipsometer capabilities are demonstrated by an accurate determination of the isotropic and anisotropic refractive indices of silicon and m-plane sapphire, respectively. Further, terahertz optical Hall effect measurements of an AlGaN/GaN high electron mobility structures were employed to extract the two-dimensional electron gas sheet density, mobility and effective mass parameters. Last, in-situ optical Hall effect measurement on epitaxial graphene in a gas cell with controllable environment, were used to study the effects of environmental doping on the mobility and carrier concentration. Paper II. Presents terahertz cavity-enhanced optical Hall measurements of the monolayer and multilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed p-type doping for monolayer graphene with a carrier density in the low 1012 cm?2 range and a carrier mobility of 1550 cm2/V·s. For the multilayer epitaxial graphene, n-type doping with a carrier density in the low 1013 cm?2 range, a mobility of 470 cm2/V·s and an effective mass of (0.14 ± 0.03) m0 were extracted. The measurements demonstrate that cavity-enhanced optical Hall effect measurements can be applied to study electronic properties of two-dimensional materials. Paper III. Terahertz cavity-enhanced optical Hall effect measurements are employed to study anisotropic transport in as-grown monolayer, quasi free-standing monolayer and quasi free-standing bilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed a strong anisotropy in the carrier mobilities of the quasi freestanding bilayer graphene. The anisotropy is demonstrated to be induced by carriers scattering at the step edges of the SiC, by showing that the mobility is higher along the step than across them. The scattering mechanism is discussed based on the results of the optical Hall effect, low-energy electron microscopy, low-energy electron diffraction and Raman measurements. Paper IV. Mid-infrared spectroscopic ellipsometry and mid-infrared optical Hall effect measurements are employed to determine the electron effective mass in an In0.33Ga0.67N epitaxial layer. The data analysis reveals slightly anisotropic effective mass and carrier mobility parameters together with the optical phonon frequencies and broadenings. Paper V. Terahertz cavity-enhanced optical Hall measurements are employed to study the free charge carrier properties in a set of AlGaN/GaN high electron mobility structures with modified interfaces. The results show that the interface structure has a significant effect on the free charge carrier mobility and that the sample with a sharp interface between an AlGaN barrier and a GaN buffer layers exhibits a record mobility of 2332±73 cm2/V·s. The determined effective mass parameters showed an increase compared to the GaN value, that is attributed the the penetration of the electron wavefunction into the AlGaN barrier layer.
Silicon Carbide
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Author : Wolfgang J. Choyke
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-04-17
Silicon Carbide written by Wolfgang J. Choyke and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-04-17 with Technology & Engineering categories.
Since the 1997 publication of "Silicon Carbide - A Review of Fundamental Questions and Applications to Current Device Technology" edited by Choyke, et al., there has been impressive progress in both the fundamental and developmental aspects of the SiC field. So there is a growing need to update the scientific community on the important events in research and development since then. The editors have again gathered an outstanding team of the world's leading SiC researchers and design engineers to write on the most recent developments in SiC. The book is divided into five main categories: theory, crystal growth, characterization, processing and devices. Every attempt has been made to make the articles as up-to-date as possible and assure the highest standards of accuracy. As was the case for earlier SiC books, many of the articles will be relevant a decade from now so that this book will take its place next to the earlier work as a permanent and essential reference volume.
Electromagnetic Simulation Using The Fdtd Method With Python
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Author : Jennifer E. Houle
language : en
Publisher: John Wiley & Sons
Release Date : 2020-01-15
Electromagnetic Simulation Using The Fdtd Method With Python written by Jennifer E. Houle and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-01-15 with Science categories.
Provides an introduction to the Finite Difference Time Domain method and shows how Python code can be used to implement various simulations This book allows engineering students and practicing engineers to learn the finite-difference time-domain (FDTD) method and properly apply it toward their electromagnetic simulation projects. Each chapter contains a concise explanation of an essential concept and instruction on its implementation into computer code. Included projects increase in complexity, ranging from simulations in free space to propagation in dispersive media. This third edition utilizes the Python programming language, which is becoming the preferred computer language for the engineering and scientific community. Electromagnetic Simulation Using the FDTD Method with Python, Third Edition is written with the goal of enabling readers to learn the FDTD method in a manageable amount of time. Some basic applications of signal processing theory are explained to enhance the effectiveness of FDTD simulation. Topics covered in include one-dimensional simulation with the FDTD method, two-dimensional simulation, and three-dimensional simulation. The book also covers advanced Python features and deep regional hyperthermia treatment planning. Electromagnetic Simulation Using the FDTD Method with Python: Guides the reader from basic programs to complex, three-dimensional programs in a tutorial fashion Includes a rewritten fifth chapter that illustrates the most interesting applications in FDTD and the advanced graphics techniques of Python Covers peripheral topics pertinent to time-domain simulation, such as Z-transforms and the discrete Fourier transform Provides Python simulation programs on an accompanying website An ideal book for senior undergraduate engineering students studying FDTD, Electromagnetic Simulation Using the FDTD Method with Python will also benefit scientists and engineers interested in the subject.
The Physics Of Semiconductors
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Author : Marius Grundmann
language : en
Publisher: Springer
Release Date : 2022-03-21
The Physics Of Semiconductors written by Marius Grundmann and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-03-21 with Technology & Engineering categories.
The 4th edition of this highly successful textbook features copious material for a complete upper-level undergraduate or graduate course, guiding readers to the point where they can choose a specialized topic and begin supervised research. The textbook provides an integrated approach beginning from the essential principles of solid-state and semiconductor physics to their use in various classic and modern semiconductor devices for applications in electronics and photonics. The text highlights many practical aspects of semiconductors: alloys, strain, heterostructures, nanostructures, amorphous semiconductors, and noise, which are essential aspects of modern semiconductor research but often omitted in other textbooks. This textbook also covers advanced topics, such as Bragg mirrors, resonators, polarized and magnetic semiconductors, nanowires, quantum dots, multi-junction solar cells, thin film transistors, and transparent conductive oxides. The 4th edition includes many updates and chapters on 2D materials and aspects of topology. The text derives explicit formulas for many results to facilitate a better understanding of the topics. Having evolved from a highly regarded two-semester course on the topic, The Physics of Semiconductors requires little or no prior knowledge of solid-state physics. More than 2100 references guide the reader to historic and current literature including original papers, review articles and topical books, providing a go-to point of reference for experienced researchers as well.
Proceedings Of The 2nd International Conference On Electronic Engineering And Renewable Energy Systems
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Author : Bekkay Hajji
language : en
Publisher: Springer Nature
Release Date : 2020-08-14
Proceedings Of The 2nd International Conference On Electronic Engineering And Renewable Energy Systems written by Bekkay Hajji and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-08-14 with Technology & Engineering categories.
This book includes papers presented at the Second International Conference on Electronic Engineering and Renewable Energy (ICEERE 2020), which focus on the application of artificial intelligence techniques, emerging technology and the Internet of things in electrical and renewable energy systems, including hybrid systems, micro-grids, networking, smart health applications, smart grid, mechatronics and electric vehicles. It particularly focuses on new renewable energy technologies for agricultural and rural areas to promote the development of the Euro-Mediterranean region. Given its scope, the book is of interest to graduate students, researchers and practicing engineers working in the fields of electronic engineering and renewable energy.
Transparent Electronics
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Author : John F. Wager
language : en
Publisher: Springer Science & Business Media
Release Date : 2007-11-20
Transparent Electronics written by John F. Wager and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-11-20 with Technology & Engineering categories.
This monograph is the first roadmap for transparent electronics. It defines and assesses what and where the field is, where it is going, and what needs to happen to get it there. Although the central focus of this monograph involves transparent electronics, many of the materials, devices, circuits, and process integration strategies discussed will be of great interest to researchers working in other emerging fields, including printed electronics, large-area electronics, low-cost electronics, and disposable electronics.
Optoelectronics And Photonics
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Author : Safa O. Kasap
language : en
Publisher: Prentice Hall
Release Date : 2013
Optoelectronics And Photonics written by Safa O. Kasap and has been published by Prentice Hall this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Technology & Engineering categories.
For one-semester, undergraduate-level courses in Optoelectronics and Photonics, in the departments of electrical engineering, engineering physics, and materials science and engineering. This text takes a fresh look at the enormous developments in electo-optic devices and associated materials.
Optical Properties Of Graphene
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Author : Rolf Binder
language : en
Publisher: World Scientific Publishing Company
Release Date : 2016
Optical Properties Of Graphene written by Rolf Binder and has been published by World Scientific Publishing Company this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Science categories.
Introductory tutorial / Rolf Binder and Nai-Hang Kwong, College of Optical Sciences and Department of Physics, University of Arizona -- Microscopic theory for the groundstate and linear optical response of novel two-dimensional materials with hexagonal symmetry / Tineke Stroucken and Stephan W. Koch, Department of Physics and Scientific Center for Material Sciences, Philipps, University Marburg -- Raman spectroscopy of graphene / Sven Reichardt (Physics and Materials Science Research Unit, Université du Luxembourg [and] JARA-FIT and 2nd Institute of Physics, RWTH Aachen University), and Ludger Wirtz (Physics and Materials Science Research Unit, Université du Luxembourg) -- Microscopic view on the ultrafast carrier dynamics in graphene / E. Malic (Department of Physics, Chalmers University of Technology [and] Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin), T. Winzer (Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin), F. Kadi (Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin), and A. Knorr (Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin) -- Theory of optical nonlinearities in graphene / Jin Luo Cheng (Brussels Photonics Team (B-PHOT), Department of Applied Physics and Photonics (IR-TONA), Vrije Universiteit Brussel [and] Department of Physics and Institute for Optical Sciences, University of Toronto), Nathalie Vermeulen (Brussels Photonics Team (B-PHOT), Department of Applied Physics and Photonics (IR-TONA), Vrije Universiteit Brussel, and John E. Sipe (Department of Physics and Institute for Optical Sciences, University of Toronto) -- Nonlinear optical experiments on graphene / Hui Zhao, Department of Physics and Astronomy, The University of Kansas -- Optical response of graphene under intense terahertz fields / J. Zhou (Center for Phononics and Thermal Energy Science, School of Physics Science and Engineering, Tongji University), and M.W. Wu (Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China) -- Nonlinear terahertz spectroscopy on multilayer graphene / Michael Woerner, Thomas Elsaesser, and Klaus Reimann, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin, Germany -- Ultrafast manipulation of terahertz waves using graphene metamaterials / Chihun In (School of Electrical and Electronic Engineering, Yonsei University, Seoul [and] Center for Quantum-Beam-based Radiation Research Korea Atomic Energy Research Institute, Daejeon), Hyunyong Choi (School of Electrical and Electronic Engineering, Yonsei University, Seoul) -- Spectroscopy of graphene at the saddle point / Daniela Wolf, Dong-Hun Chae, Tobias Utikal, Patrick Herlinger, Jurgen Smet, Harald Giessen, and Markus Lippitz -- Nonlinear saddle point spectroscopy and electron-phonon interaction in graphene / Rolf Binder (College of Optical Sciences, University of Arizona), Adam T. Roberts (U.S. Army Aviation and Missile Research, Development, and Engineering Center, Redstone Arsenal, Alabama, [and] Department of Physics, University of Arizona), Nai-Hang Kwong (College of Optical Sciences, University of Arizona), Arvinder Sandhu (College of Optical Sciences, University of Arizona), and Henry O. Everitt (U.S. Army Aviation and Missile Research, Development, and Engineering Center, Redstone Arsenal, Alabama [and] Department of Physics, University of Arizona) -- Femtosecond pulse generation with voltage-controlled graphene saturable absorbers / Isinsu Baylam (Laser Research Laboratory, Departments of Physics and Electrical-Electronics Engineering, Koç University, Istanbul, Turkey), Sarper Özharar (Department of Electrical-Electronics Engineering, Bahçesehir University, Istanbul, Turkey), Nurbek Kakenov (Department of Physics, Bilkent University, Ankara, Turkey), Coskun Kocabas (Department of Physics, Bilkent University, Ankara, Turkey), and Alphan Sennaroglu (Laser Research Laboratory, Departments of Physics and Electrical-Electronics Engineering, Koç University, Istanbul, Turkey) -- Graphene-based optical modulators / Sinan Balci (Department of Astronautical Engineering, University of Turkish Aeronautical Association, Ankara, Turkey), and Coskun Kocabas (Department of Physics, Bilkent University, Ankara, Turkey) -- The potential of graphene as a transparent electrode / Wee Shing Koh (A*STAR Institute of High Performance Computing, Singapore), Wee Kee Phua (A*STAR Institute of High Performance Computing, Singapore), and Wei Peng Goh (A*STAR Institute of Materials Research and Engineering, Singapore)
Electronic Optical And Phononic Properties Of Graphene Boron Nitride And Related Materials
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Author : CHEOL HWAN. PARK
language : en
Publisher:
Release Date : 2009
Electronic Optical And Phononic Properties Of Graphene Boron Nitride And Related Materials written by CHEOL HWAN. PARK and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
Since the isolation of graphene, a single layer of carbon atoms in honeycomb structure, in 2004, this new material has gotten huge attention from communities in physics, chemistry, materials science, and engineering not only because the charge carriers of graphene show neutrino-like linear energy dispersion as well as chiral behavior near the Dirac point but also because graphene is considered to be a promising candidate for nano- and micro-scale electronic and spintronic device applications. On the other hand, a hexagonal sheet of boron nitride has a similar honeycomb-like structure, except that the two different sublattices are occupied by boron and nitrogen atoms, respectively. Notwithstanding its structural similarity to graphene, a hexagonal boron nitride sheet is an insulator with a large bandgap and is considered to be useful to optical applications such as ultra-violet lasers. In this work, we investigate the electronic, optical, and vibrational properties of graphene, hexagonal boron nitride, and related materials such as nanotubes or nanoribbons from first-principles calculations as well as from simple model considerations. In the first chapter, we briefly review the methodologies used in our work such as density functional theory, the GW approximation, the Bethe-Salpeter equation method, and density functional perturbation theory. In the following four chapters (2-5), we discuss the calculated spectral features of graphene and compare the results mainly with recent angle-resolved photoemission experiments. In our work, we have explicitly taken into account the effects of electron-electron and electron-phonon interactions from first-principles. Our calculations reproduce some of the key experimental observations related to many-body effects, including a mismatch between the upper and lower halves of the Dirac cone and the non-trivial energy dependence of carrier linewidths on the binding energy. The following three chapters (6-8) are on bilayer graphene. In chapters 6 and 7, we discuss the effects of many-body interactions on the dynamics of electrons and phonons in bilayer graphene, in similar ways as in chapters 2 to 5. We show that the interlayer interaction between the two graphene layers change electron-phonon and electron-electron interactions. In chapter 8, we discuss the excitons in biased bilayer graphene. We show that bound excitons qualitatively change the optical response of this novel material. In the following four chapters (9-12), we discuss the interesting behaviors of charge carriers in graphene subjected to an external periodic potential. For example, we show that the carrier group velocity is anisotropically reduced and that, under certain conditions, electrons can be supercollimated. We also discuss newly generated massless Dirac fermions in graphene superlattices as well as their signatures in quantum Hall conductance measurements. In chapter 13, we discuss the possibility of generating massless Dirac fermions in a conventional two-dimensional electron gas with an external periodic potential, i.e., a way of making artificial graphene. In the last four chapters, we discuss several different aspects of boron nitride compounds. In chapter 14, we present the calculated electronic energy bandgaps and effective masses of boron nitride nanoribbons and their changes in response to a transverse electric field. In chapters 15 and 16, we discuss excitons and optical response of boron nitride nanotubes and bulk hexagonal boron nitride, respectively. Finally, in the last chapter, we discuss a novel behavior of electric dipole moment reversal upon hydrogen passivation in boron nitride as well as other III-V or II-VI compound nanostructures.