Download or read book Doping And Photophysical Properties Of II VI Semiconductor Nanocrystals written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanocrystals with sizes comparable to the corresponding bulk excitonic diameter exhibit unique size-dependent electronic and optical properties resulting from quantum confinement effect. Such nanocrystals not only allow the study of evolution of bulk properties from the molecular limit providing important fundamental understandings, but also have great technological implications, leading to intense research over the past several years. Besides tuning the crystal size in the nm regime to obtain novel properties, an additional route to derive new functionalities has been to dope transition metal ions into a semiconductor host. Thus, transition metal doped nanocrystals are of great interest since it allows two independent ways to functionalize semiconductor materials, one via the tunability of properties by size variation and other due to properties of such dopants. Chapter 1 of the thesis provide a general introduction to the subject matters dealt in with this thesis, while the necessary methodologies have been discussed in chapter 2. Chapters 3 and 4 of this thesis deal with nanocrystal doping. Following suggestions in previous literatures that the doping of nanocrystal depends strongly upon the crystal structure of the synthesized host nanocrystal, we have studied the phase-transformation between the somewhat zinc-blende and the usual wurtzite structures for CdS and CdSe nanocrystals in chapter 5. In chapter 6 we have pointed out that a gradient structure is essential to achieve nearly ideal photoluminescence efficiency using heterostructured nanocrystals and also achieved strong two-photon absorptions, adding optical bifunctionality to these nanocrystals. Finally, in chapter 7, we establish different approaches to generate white-light using nanocrystals and their unique advantages, as a first step to realizing white light emitting devices. Chapter 1 provides a brief introduction to various interesting properties and concepts relevant for the studies c.

Download or read book Semiconductor Nanocrystals written by Alexander L. Efros and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: A physics book that covers the optical properties of quantum-confined semiconductor nanostructures from both the theoretical and experimental points of view together with technological applications. Topics to be reviewed include quantum confinement effects in semiconductors, optical adsorption and emission properties of group IV, III-V, II-VI semiconductors, deep-etched and self assembled quantum dots, nanoclusters, and laser applications in optoelectronics.

Download or read book Syntheses and Applications of Mn doped II VI Semiconductor Nanocrystals written by Heesun Yang and published by . This book was released on 2003 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanocrystal Quantum Dots written by Victor I. Klimov and published by CRC Press. This book was released on 2017-12-19 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of recent advancements in colloidal nanocrystals and quantum-confined nanostructures, Nanocrystal Quantum Dots is the second edition of Semiconductor and Metal Nanocrystals: Synthesis and Electronic and Optical Properties, originally published in 2003. This new title reflects the book’s altered focus on semiconductor nanocrystals. Gathering contributions from leading researchers, this book contains new chapters on carrier multiplication (generation of multiexcitons by single photons), doping of semiconductor nanocrystals, and applications of nanocrystals in biology. Other updates include: New insights regarding the underlying mechanisms supporting colloidal nanocrystal growth A revised general overview of multiexciton phenomena, including spectral and dynamical signatures of multiexcitons in transient absorption and photoluminescence Analysis of nanocrystal-specific features of multiexciton recombination A review of the status of new field of carrier multiplication Expanded coverage of theory, covering the regime of high-charge densities New results on quantum dots of lead chalcogenides, with a focus studies of carrier multiplication and the latest results regarding Schottky junction solar cells Presents useful examples to illustrate applications of nanocrystals in biological labeling, imaging, and diagnostics The book also includes a review of recent progress made in biological applications of colloidal nanocrystals, as well as a comparative analysis of the advantages and limitations of techniques for preparing biocompatible quantum dots. The authors summarize the latest developments in the synthesis and understanding of magnetically doped semiconductor nanocrystals, and they present a detailed discussion of issues related to the synthesis, magneto-optics, and photoluminescence of doped colloidal nanocrystals as well. A valuable addition to the pantheon of literature in the field of nanoscience, this book presents pioneering research from experts whose work has led to the numerous advances of the past several years.

Download or read book Helping Observe and Tune Diffusion Using Mn2 Photophysics in Inorganic Nanocrystals After Growth written by Charles J. Barrows and published by . This book was released on 2017 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Doped inorganic crystals exhibit attractive optical, electrical, and magnetic properties that enabled the development of important modern technologies including ruby lasers and silicon microelectronics. The next frontier of doping chemistry is taking place on the nanoscale, where quantum confinement effects dramatically change the photophysical properties of semiconductors. This thesis describes recent advances in the doping of colloidal II-VI semiconductor nanocrystals known as "quantum dots." Interactions between excitonic excited states and Mn2+, a model magnetic dopant, are investigated, primarily by magnetic circular dichroism (MCD) spectroscopy. These data reveal a new mechanism of nanocrystal doping characterized by thermodynamic addition of cation + anion pairs, followed by diffusional mixing. A broad range of equilibrium compositions are achieved, from less than one to hundreds of impurities per quantum dot, and subsequent cation exchange reactions are utilized to develop a model for dopant diffusion in these nanocrystals. Unique spectroscopic signatures are demonstrated, including nonmonotonic magnetization in the low-doping regime and extraordinarily large (whopping) Zeeman splittings in more highly doped quantum dots. Collectively, these studies provide insight into the fundamental processes of diffusion and magnetic exchange on the nanoscale, and may be useful for future spintronics, spin-photonics, and solar energy conversion technologies.

Download or read book Syntheses and Application of Min doped II VI Semiconductor Nanocrystals written by Heesun Yang and published by . This book was released on 2003 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electronic and Impurity Doping in Colloidal Semiconductor Nanocrystals written by Alina Marie Schimpf and published by . This book was released on 2014 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents investigations of semiconductor nanocrystals doped with impurity ions, excess charge carriers, or both. The introduction of excess charge carriers into colloidal semiconductor nanocrystals constitutes a longstanding challenge in the development of nanocrystal building blocks for various technologies including solar cells, photovoltaic devices and electroluminescent devices. Chapter 1 discusses methods for electronic doping in semiconductor nanocrystals, focusing on photodoping and aliovent doping strategies. Of the various successful strategies for electronic doping, photodoping is particularly useful as a post-synthetic method for reversible and quantifiable tuning of carrier density. Alternatively, aliovalently doped nanocrystals are attractive due to the great stability of charge carriers. Chapter 2 presents a comparative study of conduction-band electrons in colloidal ZnO nanocrystals added via photodoping or aliovalent doping. The studies show that, although they have very similar spectroscopic properties, the reactivites of the electrons are vastly different, owing to the relative mobilities of their charge-compensating cations. Chapters 3, 4 and 5 present investigations of the ability to add excess electrons to a variety of systems via photodoping. The study in Chapter 3 shows that the maximum number of elecrons that may be added photochemically is dependent on the nanocrystal volume, such that all nanocrystals may be photodoped to the same electron density. Furthermore, the identities of the sacrifical reductant and the charge-compensating cation determine the maximum photodoping density. For the first time, alkyl borohydrides were used as sacrificial reductants to photodope ZnO, leading to much larger carrier densities than previously observed. These findings informed the first demonstration of photodoping in CdE (E= S, Se, Te) nanocrystals, presented in Chapter 4. Chapter 5 presents a combination of photodoping and aliovalent doping in In2O3 nanocrystals to investigate the redox chemistries in In2O3 and ITO nanocrystals. The study shows that all nanocrystals have the same Fermi level, and Sn4[superscript +] stabilizes that conduction band to allow accumulation of excess delocalized electrons. Moreover, regardless of Sn4[superscript +] doping and therefore of initial carrier density, all nanocrystals have the same number of electrons that may be added photochemically. These results, in conjunction with those presented in Chapters 3 and 4, suggest maximum photodoping density is thermodynamically limited, and is not an intrinsic property of the nanocrystal, nor a result of competition between productive hole-quenching and non-productive Auger recombination in the photoexcited nanocrystals. The ability to reversibly tune the carrier densities in colloidal semiconductor nanocrystals via photodoping allows new photophsyical investigations of electronically doped systems. Chapters 5 and 6 use photodoping to investigate the properties of plasmon resonances in ZnO and In2O3 nanocrystals. Chapter 5 shows that the plasmon energy is affected by both carrier density and Sn4[superscript +] doping. Chapter 6 shows that plasmons in ZnO nanocrystals are subject to quantum confinement and therefore may not be understood with a classical Drude picture. The large magnetic exchange interaction between charge carriers and magnetic dopants make diluted magnetic semiconductors (DMSs) particularly attractive for spin-based information processing. Chapter 7 uses pulsed electron paramagnetic resonance (pEPR) spectroscopy to investigate the affect of excess electrons on the Mn2[superscript +] spin dynamics in doped ZnO nancorystals, showing that Mn2[superscript +] spin relaxation is greatly accelerated by the presence of even one conduction-band electron. Chapter 8 uses pEPR to investigate the intrinsic spin dynamics of Mn2[superscript] in a variety of II-VI colloidal semiconductor nanocrystals. Finally, Chapter 9 shows the ability to tune the effective g value in DMSs at low fields using temperature.

Download or read book Synthesis of Magnetic Ion Doped II VI Benzenechalcogenolate Molecular Clusters written by Fumitoshi Kato and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Diluted magnetic semiconductor quantum dots (DMS-QDs) is a class of material prepared by introducing a small percentage of magnetic impurities to impart new magneto-optical properties to the host nanocrystal (NC). Such materials are regarded as promising candidates for their potential application in spintronic devices. The overall functionality of the DMS-QD is highly dependent on the dopant position within the host structure. A thorough understanding of the doping mechanism is, therefore, critical to gain better control over the dopant speciation in nanocrystal lattice and material properties. In this work, we utilized II-VI molecular clusters that are analogous to bulk semiconductors as model systems to obtain mechanistic insight into the doping process. More specifically, we developed new protocols for dopant speciation and to achieve precision doping in these clusters. These molecular clusters are often studied to gain a detailed understanding of the size-property relationship in quantum-confined semiconductor nanocrystals. However, studies of the doping of these structurally well-defined materials and the effect on the host properties are rare. The work presented here focuses on elucidating the solution dynamic of clusters in order to develop controlled doping strategies. The work is primarily centered on Mn2+ and Co2+ as the dopants and CdS molecular cluster as the host. Monitoring the relative peak intensity of both doped and undoped fragments of Mn2+ or Co2+ substituted CdS cluster by electrospray ionization mass spectrometry (ESI-MS) is demonstrated to be an effective method determining for dopant speciation. The cluster-cluster equilibria unraveled from our investigations led us to establish a process that allows for precision doping of clusters. Synthetic methods were formulated based on our understanding of equilibria to yield a larger sized cluster. Furthermore, the presence of impurity ions was found to have a significant impact on the equilibria as well, demonstrating that dopants participate in both cation exchange reactions and the cluster evolution. In addition, the solution dynamic of the isolated clusters was observed and shown to have higher sensitivity towards its surrounding environment. New equilibria were rapidly established once small traces of metal ions were introduced to a solution of pure clusters. The solvent and core chalcogenide ions were found to have a profound effect on the equilibrium as well as the disintegration and growth processes. The studies of solution dynamics presented in this work provide insights relevant to the development of synthetic routes for precise impurity ion doping at the molecular level and to the cluster growth mechanism.

Download or read book Single Organic Nanoparticles written by Hiroshi Masuhara and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 443 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experts describe advanced techniques for the chemical synthesis of functional organic nanoparticles and propose new methods for the characterization and manipulation of single nanoparticles. Theoretical and experimental studies of the physical and chemical properties of organic particles, semiconductor particles and liquid droplets are reported. The text gives not only scientific details but also general and historical background, applications, and future perspectives. Lucid explanations of technical terms and concepts are included where necessary.

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.

Download or read book Manganese II in Semiconductor Nanocrystals written by Vladimir A. Vlaskin and published by . This book was released on 2014 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following chapters describe the state of II-VI semiconductor nanocrystal preparation. Introduction of transition metal dopants gave rise to new materials and provided an insight into both physical and chemical properties of these semiconductor nanocrystals. Mn(II) and Co(II) dopants were used to probe the spatial position of an exciton inside Mn(II):ZnSe/CdSe core/shell nanocrystals and to show that p-d exchange still dominates s-d exchange, consistent with bulk analogues. Energy transfer between Mn(II) and excitonic states in Mn(II):ZnSe/CdZnSe with various compositions was shown to result in temperature dependent dual emission. The use of multishell ZnS/CdS/ZnS heterostructures, were shown to give both stability against chemical degradation and allowed tunability of the excitonic states. The discovery of a method to completely suppress Ostwald ripening at temperatures that still allow cations to assume their thermodynamic distributions inside the samples has laid the first step in the coming revolution of nanocrystal synthesis. Independent control over morphology and composition has settled the debate on "doping impossibility" and nanocrystals seen through the new Overton window can be placed in a dynamic equilibrium with their environment.

Download or read book Rare Earth and Transition Metal Doping of Semiconductor Materials written by Volkmar Dierolf and published by Woodhead Publishing. This book was released on 2016-01-23 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rare Earth and Transition Metal Doping of Semiconductor Material explores traditional semiconductor devices that are based on control of the electron's electric charge. This book looks at the semiconductor materials used for spintronics applications, in particular focusing on wide band-gap semiconductors doped with transition metals and rare earths. These materials are of particular commercial interest because their spin can be controlled at room temperature, a clear opposition to the most previous research on Gallium Arsenide, which allowed for control of spins at supercold temperatures. Part One of the book explains the theory of magnetism in semiconductors, while Part Two covers the growth of semiconductors for spintronics. Finally, Part Three looks at the characterization and properties of semiconductors for spintronics, with Part Four exploring the devices and the future direction of spintronics. - Examines materials which are of commercial interest for producing smaller, faster, and more power-efficient computers and other devices - Analyzes the theory behind magnetism in semiconductors and the growth of semiconductors for spintronics - Details the properties of semiconductors for spintronics

Download or read book Purification Controlled Doping and Crystal Growth of II VI Compound Semiconductors written by George N. Webb and published by . This book was released on 1977 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis of various ultra high purity compounds of the II-VI group of semiconductor materials is described and tables of analytical data for each are included. The level of impurity concentration in synthesized ZnSe has been significantly lowered. The growth of crystals of II-VI compounds from the melt in the pressure furnace is reported. Included are data concerning doping of melt grown crystals with various amounts of selected impurities. The overall quality of the melt grown ZnSe has been improved.

Download or read book Photophysical and Redox Properties of Degenerately Doped Nanocrystals written by Jose Juan Araujo and published by . This book was released on 2020 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: For the past few decades, semiconductor nanocrystals (NCs) have been the subject of intense interdisciplinary research in both fundamental science and device engineering. Their size-tunable electronic and optical properties, solution processability, and diverse synthetic chemistries make them attractive candidates for applications such as photovoltaics, photocatalysis, and lighting technologies. Besides the well-known quantum confinement effect, the introduction of dopants introduces many more opportunities to tune the electronic, optical, and magnetic properties of NCs. This thesis focuses on NCs containing excess band-like electrons, their photophysical properties, and the redox chemistries associated with these dopants in relation to their charge-compensation mechanisms. Chapter 1 outlines the basic properties of degenerately doped NCs. Methods for preparing degenerately doped NCs are discussed, along with spectroscopic and electrochemical techniques for studying their optical and electronic properties. Chapter 2 describes a new method for preparing photodoped PbSe quantum dots with high electron densities. These high doping densities allow for a careful analysis of the changes in electronic absorption, which reveal conclusive evidence for the assignment of the electronic transitions in their absorption spectra. Chapter 3 employs spectroelectrochemical potentiometry to study the redox properties of excess electrons in Sn4+:In2O3 NCs. An important difference is observed between the redox properties of electrons added by photodoping compared to aliovalent doping. These differences reflect the impact of the charge-compensation motif on determining the stability of charges in degenerately doped NCs.

Download or read book Doping Semiconductor Nanocrystals written by Lijun Zu and published by . This book was released on 2006 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantum Effects Heavy Doping and the Effective Mass written by Kamakhya Prasad Ghatak and published by World Scientific Publishing Company. This book was released on 2016-12-09 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: The importance of the effective mass (EM) is already well known since the inception of solid-state physics and this first-of-its-kind monograph solely deals with the quantum effects in EM of heavily doped (HD) nanostructures. The materials considered are HD quantum confined nonlinear optical, III-V, II-VI, IV-VI, GaP, Ge, PtSb2, stressed materials, GaSb, Te, II-V, Bi2Te3, lead germanium telluride, zinc and cadmium diphosphides, and quantum confined III-V, II-VI, IV-VI, and HgTe/CdTe super-lattices with graded interfaces and effective mass super-lattices. The presence of intense light waves in optoelectronics and strong electric field in nano-devices change the band structure of semiconductors in fundamental ways, which have also been incorporated in the study of EM in HD quantized structures of optoelectronic compounds that control the studies of the HD quantum effect devices under strong fields. The importance of measurement of band gap in optoelectronic materials under intense external fields has also been discussed in this context. The influences of magnetic quantization, crossed electric and quantizing fields, electric field and light waves on the EM in HD semiconductors and super-lattices are discussed.The content of this book finds twenty-eight different applications in the arena of nano-science and nano-technology. This book contains 200 open research problems which form the integral part of the text and are useful for both PhD aspirants and researchers in the fields of condensed matter physics, materials science, solid state sciences, nano-science and technology and allied fields in addition to the graduate courses in semiconductor nanostructures. The book is written for post-graduate students, researchers, engineers and professionals in the fields of condensed matter physics, solid state sciences, materials science, nanoscience and technology and nanostructured materials in general.

Download or read book Colloidal Semiconductor Nanocrystals Synthesis Properties and Applications written by Vladimir Lesnyak and published by Frontiers Media SA. This book was released on 2020-01-06 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: