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A Photoluminescence Scaling Study Of Cdse Znse Self Assembled Quantum Dots
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Book Synopsis A Photoluminescence Scaling Study of CdSe/ZnSe Self Assembled Quantum Dots by :
Download or read book A Photoluminescence Scaling Study of CdSe/ZnSe Self Assembled Quantum Dots written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A scaling study was conducted to determine the optical properties of CdSe/ZnSe self assembled quantum dots (SAQD) as a function of changing aperture area. To accomplish this, photoluminescence (PL) experiments were performed on a sample consisting of a (100) GaAs substrate, a 1 æm ZnSe buffer layer, 3 monolayers of CdSe (forming the SAQD), and a 50 nm ZnSe capping layer through 16 apertures ranging in area from 21.76 through 0.006 æm 2 . The PL spectra from the CdSe SAQD are composed of sharp peaks seemingly dispersed on a broad feature. Two models that explain these spectral features are a single and a multiple energy state model. The multiple energy state model assumes that both the sharp peaks and the broad feature are real, distinct characteristics of the quantum dot energy landscape, while the single energy state model assumes that the broad feature is an artifact from the overlap of the individual sharp peaks. To test this the broad and the sharp features from PL spectra were isolated and the fractional integrated intensity of the features were determined for each of the aperture areas. The ratio of the sharp/broad fractional integrated intensity was then plotted as a function of changing aperture area. If the single energy state model were correct, the broad feature would vanish with a significant reduction in aperture area. This is not the case; the area of the broad feature persists for even the smallest of aperture areas. To further test the two models, several simple simulations were performed. These simulations generate a distribution of individual sharp peaks and plot their superposition. The sharp/broad fractional integrated intensity for these simulated spectra was then plotted and compared to the results from the experimental PL spectra. None of the simulation results reproduce the experimental results. When two of the simulated spectra were added together (simulating the multiple energy state model), the sharp/broad fractional integrated intensity is very similar to the experimental results. This suggests that the multiple energy state model describes the PL spectra and the CdSe SAQD energy landscape while the single energy state model does not.
Book Synopsis Photoluminescence and Raman Scattering Studies of CdSe Self-assembled Quantum Dots Grown on ZnSe by : Heesuk Rho
Download or read book Photoluminescence and Raman Scattering Studies of CdSe Self-assembled Quantum Dots Grown on ZnSe written by Heesuk Rho and published by . This book was released on 1999 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Optical Study of the Electronic Structure of CdSe/ZnSe and CdTe/ZnTe Self Assembled Quantum Dots by :
Download or read book An Optical Study of the Electronic Structure of CdSe/ZnSe and CdTe/ZnTe Self Assembled Quantum Dots written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the excitonic structure and optical properties of single quantum dots in three different II-VI semiconductor structure systems: as-grown CdSe/ZnSe, as-grown CdTe/ZnTe, and annealed CdTe/ZnTe self-assembled quantum dots(QD) using photoluminescence(PL), micro-PL, micro-PL obtained using a sub-wavelength aperture, and PL images obtained using a Solid Immersion Lens (SIL). These experiments are performed both at zero field and magnetic field up to 3 Tesla. While in zero field, linear polarized PL are used to find exchange splitting and QD asymmetry direction of the three QD samples, in a 3 Tesla magnetic field, circular polarized PL is used to determine the g-factor and diamagnetic shift. With a solid immersion lens (SIL), we are able to directly image a large number of single QD at 6K with 400 nm spatial resolution. Using zero field measurements, we find that while the some of the QDs are symmetric, and emit completely unpolarized light, over half of the QDs are antisymmetric which are typically aligned along one of the in-plane crystallographic directions, and so emit linear polarized PL. Since polarization properties as well as spin properties such as exchange splitting, g-factor and diamagnetic coefficient are different from dot to dot due to their size and asymmetry variations, we have carried out a statistical study of these properties in order to understand what changes occur in the QDs between these three samples. The major result from this work shows that thermal annealing of CdTe dots significantly reduces the statistical variation of exchange splittings for asymmetric dots as well as the g-factors for symmetric dots. We infer that these changes result from enlargement of the CdTe dots due to interdiffusion of Zn between the barriers and the dots. This enlargement is reflected in the increase of the median distributions of the diamagnetic shifts. Moreover, in CdSe dots, where the dot size is comparable or slightly larger than the exciton Bohr diameter, we find that the variation of these parameters is reduced as well.
Book Synopsis Self-Assembled Quantum Dots by : Zhiming M Wang
Download or read book Self-Assembled Quantum Dots written by Zhiming M Wang and published by Springer Science & Business Media. This book was released on 2007-11-29 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: This multidisciplinary book provides up-to-date coverage of carrier and spin dynamics and energy transfer and structural interaction among nanostructures. Coverage also includes current device applications such as quantum dot lasers and detectors, as well as future applications to quantum information processing. The book will serve as a reference for anyone working with or planning to work with quantum dots.
Book Synopsis Investigations of Electronic Structure and Optical Properties of Ii-Vi Self-assembled Quantum Dots by : Tuan Anh Nguyen
Download or read book Investigations of Electronic Structure and Optical Properties of Ii-Vi Self-assembled Quantum Dots written by Tuan Anh Nguyen and published by . This book was released on 2006 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we use different optical and imaging spectroscopy techniques to study electronic structure and optical properties of CdTe/ZnTe and CdSe/ZnSe self-assembled quantum dots (SAQDs). We perform single dot photoluminescence excitation experiments to identify carrier excitation mechanisms in CdTe/ZnTe QDs. The first mechanism is direct excitation into the QD excited states followed by relaxation to the ground state and the second mechanism is direct excitation into the QD ground states through LO phonon-assisted absorption. We then execute resonant PL measurements for both CdTe and CdSe QD ensembles to study the dependence of exciton-LO phonon coupling on QD size in these II-VI SAQDs. We shown that the strength of exciton-LO phonon coupling increases significantly for QDs with lateral sizes smaller than the exciton Bohr radius (e.g. as-grown CdTe QDs) while for larger QDs (e.g. CdSe or CdTe annealed) it is almost independent of the QD emission energy, and therefore presumably of the QD size. In order to study electronic coupling between SAQDs, we setup imaging experiments with the use of a hemisphere solid immersion lens. While the PLE imaging measurements show the existence two-dimensional platelets with a typical size of about 500 nm which provide spatially extended but strong localized states through which different QDs could be populated simultaneously, the spatially resolved imaging data demonstrates a complete 2D map of those platelets. These results are further supported by computational calculations based on finite element analysis. Low temperature exciton spin relaxation in symmetric CdTe SAQDs has been thoroughly studied by means of cw polarized magneto-PL and polarized time-resolved PL spectroscopies. We find that the degeneracy of exciton energy levels has a strong influence on the spin transition. When the exciton spin states in QDs are degenerate, the spin relaxation time is much shorter than the exciton recombination time. In contrast, if this degeneracy is removed, either by asymmetry or an external magnetic field, the spin relaxation time becomes much longer than the exciton recombination time. Using simple rate equation models, we estimate exciton spin relaxation times equal to 4.8 ns and 50 ps for non-degenerate and degenerate QD states, respectively.
Book Synopsis State-of-the-Art of Quantum Dot System Fabrications by : Ameenah Al-Ahmadi
Download or read book State-of-the-Art of Quantum Dot System Fabrications written by Ameenah Al-Ahmadi and published by BoD – Books on Demand. This book was released on 2012-06-13 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book "State-of-the-art of Quantum Dot System Fabrications" contains ten chapters and devotes to some of quantum dot system fabrication methods that considered the dependence of shape, size and composition parameters on growth methods and conditions such as temperature, strain and deposition rates. 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.
Book Synopsis Advances in Condensed Matter and Materials Research by : Francois Gerard
Download or read book Advances in Condensed Matter and Materials Research written by Francois Gerard and published by Nova Publishers. This book was released on 2001 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nine articles written especially for the series synthesize international research in condensed matter. Among the topics are fiber debonding and bridging toughening in fiber-reinforced brittle matrix composites, analyzing the electron transport phenomena in high- temperature superconductivity materials by studying the band spectrum and its transformation under doping by different impurities, a functional integral approach in superconductivity theory, dye molecules in zeolite L nano crystals for efficient light harvesting, luminescent properties of some substituted 1,8 naphthyridines, and the discrete dependence of powder steels properties on porosity. No information is provided about future volumes. c. Book News Inc.
Download or read book Quantum Dots written by Ameenah Al-Ahmadi and published by BoD – Books on Demand. This book was released on 2012-04-04 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book “Quantum dots: A variety of a new applications” provides some collections of practical applications of quantum dots. This book is divided into four sections. In section 1 a review of the thermo-optical characterization of CdSe/ZnS core-shell nanocrystal solutions was performed. The Thermal Lens (TL) technique was used, and the thermal self-phase Modulation (TSPM) technique was adopted as the simplest alternative method. Section 2 includes five chapters where novel optical and lasing application are discussed. In section 3 four examples of quantum dot system for different applications in electronics are given. Section 4 provides three examples of using quantum dot system for biological applications. This is a collaborative book sharing and providing fundamental research such as the one conducted in Physics, Chemistry, Biology, Material Science, Medicine 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.
Book Synopsis Semiconductor Quantum Dots by : Yasuaki Masumoto
Download or read book Semiconductor Quantum Dots written by Yasuaki Masumoto and published by Springer Science & Business Media. This book was released on 2002-05-28 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Growth of Self Organized Quantum Dots / J.-S. Lee / - Excitonic Structures and Optical Properties of Quantum Dots / Toshihide Takagahara / - Electron-Phonon Interactions in Semiconductor Quantum Dots / Toshihide Takagahara / - Micro-Imaging and Single Dot Spectroscopy of Self Assembled Quantum Dots / Mitsuru Sugisaki / - Persistent Spectral Hole Burning in Semiconductor Quantum Dots / Yasuaki Masumoto / - Dynamics of Carrier Relaxation in Self Assembled Quantum Dots / Ivan V. Ignatiev, Igor E. Kozin / - Resonant Two-Photon Spectroscopy of Quantum Dots / Alexander Baranov / - Homogeneous Width of Confined Excitons in Quantum Dots - Experimental / Yasuaki Masumoto / - Theory of Exciton Dephasing in Semiconductor Quantum Dots / Toshihide Takagahara / - Excitonic Optical Nonlinearity and Weakly Correlated Exciton-Pair States / Selvakumar V. Nair, Toshihide Takagahara / - Coulomb Effects in the Optical Spectra of Highly Excited Semiconductor Quantum Dots / Selvakumar V. Nair / - Device ...
Book Synopsis Optical and Electrical Properties of Single Self-Assembled Quantum Dots in Lateral Electric Fields by : Malte Huck
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 [...]
Book Synopsis Nanotechnology Abstracts by : Eugene V. Dirote
Download or read book Nanotechnology Abstracts written by Eugene V. Dirote and published by Nova Publishers. This book was released on 2002 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanotechnology is a 'catch-all' description of activities at the level of atoms and molecules that have applications in the real world. A nanometre is a billionth of a metre, that is, about 1/80,000 of the diameter of a human hair, or 10 times the diameter of a hydrogen atom. Nanotechnology is now used in precision engineering, new materials development as well as in electronics; electromechanical systems as well as mainstream biomedical applications in areas such as gene therapy, drug delivery and novel drug discovery techniques. This book presents carefully selected abstracts of the last 5 years in this frontier field. Special access is provide by author, title and subject indexes.
Book Synopsis Materials Science & Engineering by :
Download or read book Materials Science & Engineering written by and published by . This book was released on 2003 with total page 1290 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Study of Self-assembled ZnSe Quantum Dots Under the Influences of the Growth Temperature and Cap Layer Thickness by :
Download or read book Study of Self-assembled ZnSe Quantum Dots Under the Influences of the Growth Temperature and Cap Layer Thickness written by and published by . This book was released on 2003 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Atomistic Aspects of Epitaxial Growth by : Miroslav Kotrla
Download or read book Atomistic Aspects of Epitaxial Growth written by Miroslav Kotrla and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Epitaxial growth lies at the heart of a wide range of industrial and technological applications. Recent breakthroughs, experimental and theoretical, allow actual atom-by-atom manipulation and an understanding of such processes, opening up a totally new area of unprecedented nanostructuring. The contributions to Atomistic Aspects of Epitaxial Growth are divided into five main sections, taking the reader from the atomistic details of surface diffusion to the macroscopic description of epitaxial systems. many of the papers contain substantial background material on theoretical and experimental methods, making the book suitable for both graduate students as a supplementary text in a course on epitaxial phenomena, and for professionals in the field.
Book Synopsis Core/Shell Quantum Dots by : Xin Tong
Download or read book Core/Shell Quantum Dots written by Xin Tong and published by Springer Nature. This book was released on 2020-07-01 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book outlines various synthetic approaches, tuneable physical properties, and device applications of core/shell quantum dots (QDs). Core/shell QDs have exhibited enhanced quantum yield (QY), suppressed photobleaching/blinking, and significantly improved photochemical/physical stability as compared to conventional bare QDs. The core-shell structure also promotes the easy tuning of QDs’ band structure, leading to their employment as attractive building blocks in various optoelectronic devices. The main objective of this book is to create a platform for knowledge sharing and dissemination of the latest advances in novel areas of core/shell QDs and relevant devices, and to provide a comprehensive introduction and directions for further research in this growing area of nanomaterials research.
Book Synopsis International Conference on Thin Film Physics and Applications by :
Download or read book International Conference on Thin Film Physics and Applications written by and published by . This book was released on 2000 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Semiconductor Nanocrystal Quantum Dots by : Andrey Rogach
Download or read book Semiconductor Nanocrystal Quantum Dots written by Andrey Rogach and published by Springer Science & Business Media. This book was released on 2008-09-02 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to specifically focus on semiconductor nanocrystals, and address their synthesis and assembly, optical properties and spectroscopy, and potential areas of nanocrystal-based devices. The enormous potential of nanoscience to impact on industrial output is now clear. Over the next two decades, much of the science will transfer into new products and processes. One emerging area where this challenge will be very successfully met is the field of semiconductor nanocrystals. Also known as colloidal quantum dots, their unique properties have attracted much attention in the last twenty years.
