Download or read book Symmetry Effects in Optical Properties of Single Semconductor Quantum Dots written by Katarzyna Kowalik and published by . This book was released on 2007 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cette thèse porte sur l'étude des effets de réduction de la symétrie des boîtes quantiques de semiconducteur auto-assemblées III-V et II-VI sur leurs propriétés optiques, et tout particulièrement sur la levée de dégénérescence des états excitoniques, qui joue un rôle primordial pour intriquer en polarisation des photons à partir de la cascade radiative d'un biexciton. Nous avons d'une part étudié l'influence d'un champ électrique appliqué soit latéralement (dans le plan des boîtes quantiques), soit parallèlement (à leur direction de croissance), et d'autre part un champ magnétique latéral. On montre que l'asymétrie des boîtes peut être efficacement compensée en déformant les fonctions d'onde excitoniques par un champ électrique, tandis qu'un champ magnétique permet par effet Zeeman de réduire la structure fine des excitons. Enfin, la cohérence du pseudo-spin des excitons, autre pré-requis à l'intrication en polarisation, est étudiée par des expériences d'orientation/alignement optique et de conversion de polarisation en fonction d'un champ magnétique longitudinal. Nos résultats démontrent que cette cohérence quantique ne relaxe pas à l'échelle du temps de vie radiatif des excitons.
Download or read book Fingerprints in the Optical and Transport Properties of Quantum Dots written by Ameenah Al-Ahmadi and published by BoD – Books on Demand. This book was released on 2012-06-13 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book "Fingerprints in the optical and transport properties of quantum dots" provides novel and efficient methods for the calculation and investigating of the optical and transport properties of quantum dot systems. This book is divided into two sections. In section 1 includes ten chapters where novel optical properties are discussed. In section 2 involve eight chapters that investigate and model the most important effects of transport and electronics properties of quantum dot systems This is a collaborative book sharing and providing fundamental research such as the one conducted in Physics, Chemistry, Material Science, with a base text that could serve as a reference in research by presenting up-to-date research work on the field of quantum dot systems.
Download or read book Experimental and Theoretical Study of the Optical Properties of Semiconductor Quantum Dots written by Gero Nootz and published by . This book was released on 2010 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this dissertation is to gain a better understanding of the unique electronic structure of lead salt quantum dots (QDs) and its influences on the nonlinear optical (NLO) properties as well as the time dynamics of the photogenerated charge carriers. A variety of optical techniques such as Z-scan, two-photon excited fluorescence and time-resolved pump probe spectroscopy are used to measure these properties. The one-photon as well as the degenerate and nondegenerate two-photon absorption (2PA) spectra are measured and the electronic wave functions from a four-band envelope function formalism are used to model the results. We observe local maxima in the 2PA spectra for QD samples of many different sizes at energies where only 1PA is predicted by the model. This is similar to the previously measured transitions in the 1PA spectra which are not predicted by the model but accrue at the energies of the two-photon allowed transitions. Most importantly we observe 2PA peaks for all samples at the energy of the first one-photon allowed transition. This result can only be understood in terms of symmetry breaking and therefore is strong evidence that other transitions, not predicted by the model if the selection rules are left intact, also have the origin in the lifted spatial symmetry of the wave functions. On the other hand, the uniquely symmetric eigenenergies of these quantum-confined energy states in the conduction and valance bands explain the observed trend toward larger two-photon cross-sections as the quantum confinement is increased in smaller QDs. Moreover, this unique feature is shown to reduce the possible relaxation channels for photoexcited carriers, which is confirmed experimentally by the reduced carrier relaxation rate as compared to CdSe QDs which lack this symmetry. Carrier multiplication (CM), a process in which several electrons are excited by the absorption of a single photon is studied in PbS QDs. We show that for PbS QDs with radius smaller than 2.5 nm the parameters of CM get very close to the theoretical optimum. Next-generation solar cells operating under these ideal conditions could potentially have conversion efficiency of up to 42%. This compares favorably to the 30% efficiency limit of a single junction silicon solar cell.
Download or read book Optical and Electrical Properties of Single Self Assembled Quantum Dots in Lateral Electric Fields written by Malte Huck and published by diplom.de. This book was released on 2010-03-25 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inhaltsangabe:Abstract: Chapter 1: In this thesis we investigate the optical properties of self-assembled quantum dots exposed to a lateral electric field. As a result of the electric field the wave functions of electrons and holes inside the quantum dot are manipulated, which makes it possible to tune their energy levels and control the optical properties of the system. The possibility of tuning the emission energy of different few particle states using this method makes this system very promising for the use of a source of polarization entangled photons as discussed in the following sections. In Section 1.1 the concept of entangled states is introduced together with a brief historical overview. The possibility of using the exciton biexciton cascade of a self-assembled quantum dot for the generation of entangled photon pairs is presented in Section 1.2. Chapter 2: In this chapter we introduce the concept of quantum dots and demonstrate their optical emission properties. In Section 2.1 the quantum dot is introduced as a three-dimensional charge carrier trap. Several types of quantum dots are presented in an overview. In Section 2.2 we discuss the physical effects that occur on the way from bulk semiconductor material to the three-dimensional charge carrier confinement in the case of quantum dots. The growth of self-assembled quantum dot samples is the topic of Section 2.3, where the technique of molecular beam epitaxy is introduced (Section 2.3.1). This technique is used to grow the semiconductor quantum dots via heteroepitaxy in the Stranski-Krastanov growth mode (Section 2.3.2). Quantum dots are commonly referred to as artificial atoms due to their atomlike emission features. The origin for this expression is explained in Section 2.4 on the basis of the energetic structure of self-assembled quantum dots. The optical properties of quantum dots are discussed in Section 2.5, beginning with an introduction to the experimental setup that has been used to investigate the quantum dots during this thesis (Section 2.5.1). Different optical excitation modes are presented in Section 2.5.2 and in Section 2.5.3 we discuss, how to achieve a low enough quantum dot density on the analyzed samples. Section 2.5.4 deals with the photoluminescence of different exciton states and in Section 2.5.5 we present how these lines can be identified via power dependent measurements. Finally, the concept of initial charges in self-assembled quantum dots is presented in [...]
Download or read book Semiconductor Quantum Dots written by Y. Masumoto and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor quantum dots represent one of the fields of solid state physics that have experienced the greatest progress in the last decade. Recent years have witnessed the discovery of many striking new aspects of the optical response and electronic transport phenomena. This book surveys this progress in the physics, optical spectroscopy and application-oriented research of semiconductor quantum dots. It focuses especially on excitons, multi-excitons, their dynamical relaxation behaviour and their interactions with the surroundings of a semiconductor quantum dot. Recent developments in fabrication techniques are reviewed and potential applications discussed. This book will serve not only as an introductory textbook for graduate students but also as a concise guide for active researchers.
Download or read book Single Semiconductor Quantum Dots written by Peter Michler and published by Springer Science & Business Media. This book was released on 2009-06-13 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews recent advances in the field of semiconductor quantum dots via contributions from prominent researchers in the scientific community. Special focus is given to optical, quantum optical, and spin properties of single quantum dots.
Download or read book Effect of Static Electric Fields on The Electronic And Optical Properties of Layered Semiconductor Nanostructures written by Volodya A. Harutyunyan and published by Bentham Science Publishers. This book was released on 2015-11-04 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume investigates the theory of the effect of static electric fields on one-electron states in. nanocylindrical and nanospherical heterolayers and quantized semiconductor films. Homogeneous external electrostatic field for all these structures has been considered as a "universal" modulating factor. For structures with radial symmetry, a study on the influence of radial static field and the electric field of a charged ring on one-electron states is presented. Chapters focusing on homogeneous field effect on low-dimensional excitonic states in the quantized films and quantum wires - in both wide bandgap and narrowband semiconductors - are also included. Other contents include calculations weak, moderate and strong electric fields, quantum-mechanical approximation and perturbation theory, the quasi-classical approximation (WKB method). Readers will benefit from the varied methodological to the subject which gives them a concrete analytical framework to solve problems related to nanoscale semiconductor design. The reference should prove to be useful to academics and professionals working in semiconductor nanoelectronics research and development.
Download or read book Semiconductor Quantum Dots written by Ladislaus B nyai and published by World Scientific. This book was released on 1993 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor Quantum Dots presents an overview of the background and recent developments in the rapidly growing field of ultrasmall semiconductor microcrystallites, in which the carrier confinement is sufficiently strong to allow only quantized states of the electrons and holes. The main emphasis of this book is the theoretical analysis of the confinement induced modifications of the optical and electronic properties of quantum dots in comparison with extended materials. The book develops the theoretical background material for the analysis of carrier quantum-confinement effects, introduces the different confinement regimes for relative or center-of-mass motion quantization of the electron-hole-pairs, and gives an overview of the best approximation schemes for each regime. A detailed discussion of the carrier states in quantum dots is presented and surface polarization instabilities are analyzed, leading to the self-trapping of carriers near the surface of the dots. The influence of spin-orbit coupling on the quantum-confined carrier states is discussed. The linear and nonlinear optical properties of small and large quantum dots are studied in detail and the influence of the quantum-dot size distribution in many realistic samples is outlined. Phonons in quantum dots as well as the influence of external electric or magnetic fields are also discussed. Last but not least the recent developments dealing with regular systems of quantum dots are also reviewed. All things included, this is an important piece of work on semiconductor quantum dots not to be dismissed by serious researchers and physicists.
Download or read book Optical Properties of Semiconductor Quantum Dots written by Ulrike Woggon and published by Springer. This book was released on 1997 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an overview of the current understanding of the physics of zero-dimensional semiconductors. It concentrates mainly on quantum dots of wide-gap semiconductors, but touches also on zero-dimensional systems based on silicon and III-V materials. After providing the reader with a theoretical background, the author illustrates the specific properties of three-dimensionally confined semiconductors, such as the size dependence of energy states, optical transitions, and dephasing mechanisms with the results from numerous experiments in linear and nonlinear spectroscopy. Technological concepts of the growth concepts and the potential of this new class of semiconductor materials for electro-optic and nonlinear optical devices are also discussed.
Download or read book High Resolution Optical Spectroscopy of Single Quantum Dots and Cavity QED Effects and Lasing in Quantum Dot Microdisk Resonator Structures written by and published by . This book was released on 2000 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project was initiated to study quantum electrodynamic effects (QED) on the interaction between quantum dots and the electromagnetic field. Investigations of quantized matter-field interactions involving self-assembled quantum dots required an advance in the understanding of the electronic structure and optical properties of strained quantum dots. Consequently much of the research carried out under this grant centered on clarifying these issues. Problems investigated included: optimization of the growth process by which the quantum dots were formed; physical characterization of the microstructure of the quantum dots so as to identify their symmetries and to enable the creation of appropriate electronic structure models; the use of these results to calculate electronic structure; and spectroscopic tests of the models.
Download or read book Quantum Dot Heterostructures written by Dieter Bimberg and published by John Wiley & Sons. This book was released on 1999-03-17 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Da die Nachfrage nach immer schnelleren und kleineren Halbleiterbauelementen stetig wächst, sind Quanten-Dots und -Pyramiden rasant in den Mittelpunkt der Halbleiterforschung gerückt. Dieses Buch vermittelt einen umfassenden Überblick über den aktuellen Forschungsstand auf diesem Gebiet. Behandelt werden u.a. Fragen, wie Strukturen aufgebaut, wie sie charakterisiert werden und wie sie die Leistungsfähigkeit der Bauelemente bestimmen. (11/98)
Download or read book Single Quantum Dots written by Peter Michler and published by Springer Science & Business Media. This book was released on 2003-12-09 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: Special focus is given to the optical and electronic properties of single quantum dots due to their potential applications in devices operating with single electrons and/or single photons. This includes quantum dots in electric and magnetic fields, cavity-quantum electrodynamics, nonclassical light generation, and coherent optical control of excitons.
Download or read book Semiconductor and Metal Nanocrystals written by Victor I. Klimov and published by CRC Press. This book was released on 2003-11-07 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast technological potential of nanocrystalline materials, as well as current intense interest in the physics and chemistry of nanoscale phenomena, has led to explosive growth in research on semiconductor nanocrystals, also known as nanocrystal quantum dots, and metal nanoparticles. Semiconductor and Metal Nanocrystals addresses current topics impacting the field including synthesis and assembly of nanocrystals, theory and spectroscopy of interband and intraband optical transitions, single-nanocrystal optical and tunneling spectroscopies, electrical transport in nanocrystal assemblies, and physical and engineering aspects of nanocrystal-based devices. Written by experts who have contributed pioneering research, this reference comprises key advances in the field of semiconductor nanocrystal quantum dots and metal nanoparticles over the past several years. Focusing specifically on nanocrystals generated through chemical techniques, Semiconductor and Metal Nanocrystals Merges investigative frontiers in physics, chemistry, and engineering Documents advances in nanocrystal synthesis and assembly Explores the theory of electronic excitations in nanoscale particles Presents comprehensive information on optical spectroscopy of interband and intraband optical transitions Reviews data on single-nanocrystal optical and tunneling spectroscopies Weighs controversies related to carrier relaxation dynamics in ultrasmall nanoparticles Discusses charge carrier transport in nanocrystal assemblies Provides examples of lasing and photovoltaic nanocrystal-based devices Semiconductor and Metal Nanocrystals is a must read for scientists, engineers, and upper-level undergraduate and graduate students interested in the physics and chemistry of nanoscale semiconductor and metal particles, as well as general nanoscale science. About the Editor: VICTOR I. KLIMOV is Team Leader, Softmatter Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory, New Mexico. The recipient of the Los Alamos Fellows Prize (2000), he is a Fellow of the Alexander von Humboldt Foundation, leader of the Nanophotonics and Nanoelectronics Thrust of the Center for Integrated Nanotechnologies (U.S. Department of Energy), a member of the Los Alamos Board of Governors of the Institute for Complex Adaptive Matter, and a member of the Steering Committee for the Los Alamos Quantum Institute. He received the M.S. (1978), Ph.D. (1981), and Dr. Sci. (1993) degrees from Moscow State University, Russia.
Download or read book Quantum Dots written by T. Chakraborty and published by Elsevier. This book was released on 1999-11-30 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with the electronic and optical properties of two low-dimensional systems: quantum dots and quantum antidots and is divided into two parts. Part one is a self-contained monograph which describes in detail the theoretical and experimental background for exploration of electronic states of the quantum-confined systems. Starting from the single-electron picture of the system, the book describes various experimental methods that provide important information on these systems. Concentrating on many-electron systems, theoretical developments are described in detail and their experimental consequences are also discussed. The field has witnessed an almost explosive growth and some of the future directions of explorations are highlighted towards the end of the monograph. The subject matter is dealt with in such a way that it is both accessible to beginners and useful for expert researchers as a comprehensive review of most of the developments in the field.Furthermore the book contains 37 reprinted articles which have been selected to provide a first-hand picture of the overall developments in the field. The early papers have been arranged to portray the developments chronologically, and the more recent papers provide an overview of future direction in the research.
Download or read book Quantum Dots written by Elena Borovitskaya and published by World Scientific. This book was released on 2002-07-08 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, leading experts on quantum dot theory and technology provide comprehensive reviews of all aspects of quantum dot systems. The following topics are covered: (1) energy states in quantum dots, including the effects of strain and many-body effects; (2) self-assembly and self-ordering of quantum dots in semiconductor systems; (3) growth, structures, and optical properties of III-nitride quantum dots; (4) quantum dot lasers.
Download or read book Theory of Semiconductor Quantum Dots written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantum Dot Molecules written by Jiang Wu and published by Springer Science & Business Media. This book was released on 2013-10-28 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: A quantum dot molecule (QDM) is composed of two or more closely spaced quantum dots or “artificial atoms.” In recent years, QDMs have received much attention as an emerging new artificial quantum system. The interesting and unique coupling and energy transfer processes between the “artificial atoms” could substantially extend the range of possible applications of quantum nanostructures. This book reviews recent advances in the exciting and rapidly growing field of QDMs via contributions from some of the most prominent researchers in this scientific community. The book explores many interesting topics such as the epitaxial growth of QDMs, spectroscopic characterization, and QDM transistors, and bridges between the fundamental physics of novel materials and device applications for future information technology. Both theoretical and experimental approaches are considered. Quantum Dot Molecules can be recommended for electrical engineering and materials science department courses on the science and design of advanced and future electronic and optoelectronic devices.
