Download or read book Magnetooptical properties of dilute nitride nanowires written by Mattias Jansson and published by Linköping University Electronic Press. This book was released on 2020-06-18 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured III-V semiconductors have emerged as one of the most promising materials systems for future optoelectronic applications. While planar III-V compounds are already at the center of the ongoing lighting revolution, where older light sources are replaced by modern white light LEDs, fabricating such materials in novel architectures, such as nanowires and quantum dots, creates new possibilities for optoelectronic applications. Not only do nanoscale structures allow the optically active III-V materials to be integrated with silicon microelectronics, but they also give rise to new fascinating properties inherent to the nanoscale. One of the key parameters considered when selecting materials for applications in light-emitting and photovoltaic devices is the band gap energy. While alloying of conventional III-V materials provides a certain degree of band gap tunability, a significantly enhanced possibility of band gap engineering is offered by so-called dilute nitrides, where incorporation of a small percentage of nitrogen into III-V compounds causes a dramatic down-shift of the conduction band edge. In addition, nitrogen-induced splitting of the conduction band in dilute nitrides can be utilized in intermediate band solar cells, belonging to the next generation of photovoltaic devices. For any material to be viable for optoelectronic applications, detailed knowledge of the electronic structure of the material, as well as a good understanding of carrier recombination processes is vital. For example, alloying may not only cause changes in the electronic structure but can also induce disorder. Disorder-induced potential fluctuations may alter charge carrier and exciton dynamics, and may even induce quantum confinement. Moreover, various defects in the material may introduce detrimental non-radiative (NR) states in the band gap deteriorating radiative efficiency. It is evident that, due to their different growth mechanisms, such properties could be markedly different in nanowires as compared to their planar counterparts. In this thesis, I aim to describe the electronic structure of dilute nitride nanowires, and its effects on the optical properties. Firstly, we investigate the electronic structure, and the structural and optical properties of novel GaNAsP nanowires, with a particular focus on the dominant recombination channels in the material. Secondly, we show how short-range fluctuations in the nitrogen content lead to the formation of quantum dots in dilute nitride nanowires, and investigate their electronic structure. Finally, we investigate the combined charge carrier and exciton dynamics of the quantum dots and effects of defects in their surroundings. Before considering individual sources of NR recombination, it is instructive to investigate the overall effects of nitrogen incorporation on the structural properties of the nanowires. In Paper I, we show that nitrogen incorporation up to 0.16% in Ga(N)AsP nanowires does not affect the overall structural quality of the material, nor does nitrogen degrade the good compositional uniformity of the nanowires. It is evident from our studies, however, that nitrogen incorporation has a strong and complex effect on recombination processes. We first show that nitrogen incorporation in GaNAsP nanowires reduces the NR recombination at room temperature as compared to the nitrogen-free nanowires (Paper I). This is in stark contrast to dilute nitride epilayers, where nitrogen incorporation enhances NR recombination. The reason for this difference is that in nanowires the surface recombination, rather than recombination via point defects, is the dominant NR recombination mechanism. We suggest that the nitrogen-induced suppression of the NR surface recombination in the nanowires is due to nitridation of the nanowire surface. Another NR recombination channel common in III-V nanowires is caused by the presence of structural defects, such as rotational twin planes and stacking faults. Interestingly, while nitrogen incorporation does not appear to affect the density of such structural defects, increasing nitrogen incorporation reduces the NR recombination via the structural defects (Paper II). This is explained by competing trapping of excited carriers/excitons to the localized states characteristic to dilute nitrides, and at nitrogen-induced NR defects. This effect is, however, only present at cryogenic temperatures, while at room temperature the NR recombination via the structural defects is not the dominant recombination channel. Importance of point defects in carrier recombination is highlighted in Paper III. Using the optically detected magnetic resonance technique, we show that gallium vacancies (VGa) that are formed within the nanowire volume act as efficient NR recombination centers, degrading optical efficiency of the Ga(N)AsP-based nanowires. Interestingly, while the defect formation is promoted by nitrogen incorporation, it is also readily present in ternary GaAsP nanowires. This contrasts with previous studies on planar structures, where VGa was not formed in the absence of nitrogen, unless subjected to irradiation by high-energy particles or heavy n-type doping. This, again, highlights how the defect formation is strikingly different in nanowires as compared to planar structures, likely due to the different growth processes. Potential fluctuations in the conduction band, caused by non-uniformity of the nitrogen incorporation, is characteristic to dilute nitrides and is known to cause exciton/carrier localization. We find that in dilute nitride nanowires, such fluctuations at the short range cause three-dimensional quantum confinement of excitons, resulting in optically active quantum dots with spectrally ultranarrow and highly polarized emission lines (Paper IV). A careful investigation of such quantum dots reveals that their properties are strongly dependent on the host material (Papers V, VI). While the principal quantization axis of the quantum dots formed in the ternary GaNAs nanowires is preferably oriented along the nanowire axis (Paper V), it switches to the direction perpendicular to the nanowire axis in the quaternary GaNAsP nanowires (Paper VI). Another aspect illustrating the influence of the host material on the quantum-dot properties is the electronic character of the captured hole. In both alloys, we show coexistence of quantum dots where the captured holes are of either a pure heavy-hole character or a mixed light-hole and heavy-hole character. In the GaNAs quantum dots, the main cause of the light- and heavy-hole splitting is uniaxial tensile strain induced by a combination of lattice mismatch with the nanowire core and local alloy fluctuations (Paper V). In the GaNAsP quantum dots, however, we suggest that the main mechanism for the light- and heavy-hole splitting is local fluctuations in the P/As ratio (Paper VI). Using time correlation single-photon counting, we show that the quantum dots in these dilute nitride nanowires behave as single photon emitters (Paper VI), confirming the three-dimensional quantum confinement of the emitters. Finally, since the quantum dots are formed by fluctuations mainly in the conduction band, only electrons are preferentially captured in the 0D confinement potential, whereas holes are expected to be mainly localized through the Coulomb interaction once an electron is captured by the quantum dot. In Paper VII, we investigate this rather peculiar capture mechanism, which we show to lead to unipolar, negative charging of the quantum dot. Moreover, we demonstrate that carrier capture by some quantum dots is strongly affected by the presence of defects in their local surroundings, which further alters the charge state of the quantum dot, where formation of the negatively charged exciton is promoted at the expense of its neutral counterpart. This underlines that the local surroundings of the quantum dots may greatly affect their properties and illustrates a possible way to exploit the defects for charge engineering of the quantum dots. In summary, in this thesis work, we identify several important non-radiative recombination processes in dilute nitride nanowires that can undermine the potential of these novel nanostructures for future optoelectronic applications. The gained knowledge could be found useful for designing strategies to mitigate these harmful processes, thereby improving the efficiency of future light-emitting and photovoltaic devices based on these nanowires. Furthermore, we uncover a set of optically bright quantum dot single-photon emitters embedded in the dilute nitride nanowires, and reveal their unusual electronic structure with strikingly different confinement potentials between electrons and holes. Our findings open a new pathway for charge engineering of the quantum dots in nanowires, attractive for applications in e.g. quantum computation and optical switching.

Download or read book BREAD written by Cesare Manetti and published by Sapienza Università Editrice. This book was released on 2017-05-01 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bread contains human knowledge: from knowledge concerning fertility of the land to farming methods harvesting, and seed processing, not to mention the different possibilities of consumption of cereals and the different ways in which they are cooked. In bread, we find all those components: the transformation of the natural landscape, technological and economic development which over the centuries have led to the building of a social organization, with a precise division and distribution of tasks and roles.

Download or read book The Present and Future of Jus Cogens written by Enzo Cannizzaro and published by Sapienza Università Editrice. This book was released on 2015-12-31 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the contributions presented to the first edition of the Gaetano Morelli Lectures, held in the Spring of 2014 on “the Present and Future of Jus Cogens”. The first two Chapters reproduce the two general courses by Christian Tomuschat and by Pierre-Marie Dupuy. Two short Chapters, by Enzo Cannizzaro and by Beatrice Bonafé, address topics dealt with in the final seminar class.

Download or read book Semiconductor Nanowires I Growth and Theory written by and published by Academic Press. This book was released on 2015-11-26 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor Nanowires: Part A, Number 93 in the Semiconductor and Semimetals series, focuses on semiconductor nanowires. - Contains comments from leading contributors in the field semiconductor nanowires - Provides reviews of the most important recent literature - Presents a broad view, including an examination of semiconductor nanowires - Comprises up to date advancements in the technological development of nanowire devices and systems, and is comprehensive enough to be used as a reference book on nanowires as well as a graduate student text book

Download or read book Fundamental Properties of Semiconductor Nanowires written by Naoki Fukata and published by Springer Nature. This book was released on 2020-11-16 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers virtually all aspects of semiconductor nanowires, from growth to related applications, in detail. First, it addresses nanowires’ growth mechanism, one of the most important topics at the forefront of nanowire research. The focus then shifts to surface functionalization: nanowires have a high surface-to-volume ratio and thus are well-suited to surface modification, which effectively functionalizes them. The book also discusses the latest advances in the study of impurity doping, a crucial process in nanowires. In addition, considerable attention is paid to characterization techniques such as nanoscale and in situ methods, which are indispensable for understanding the novel properties of nanowires. Theoretical calculations are also essential to understanding nanowires’ characteristics, particularly those that derive directly from their special nature as one-dimensional nanoscale structures. In closing, the book considers future applications of nanowire structures in devices such as FETs and lasers.

Download or read book Semiconductor Nanowires II Properties and Applications written by and published by Academic Press. This book was released on 2016-01-11 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor Nanowires: Part B, and Volume 94 in the Semiconductor and Semimetals series, focuses on semiconductor nanowires. - Includes experts contributors who review the most important recent literature - Contains a broad view, including examination of semiconductor nanowires

Download or read book Novel Compound Semiconductor Nanowires written by Fumitaro Ishikawa and published by CRC Press. This book was released on 2017-10-17 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: One dimensional electronic materials are expected to be key components owing to their potential applications in nanoscale electronics, optics, energy storage, and biology. Besides, compound semiconductors have been greatly developed as epitaxial growth crystal materials. Molecular beam and metalorganic vapor phase epitaxy approaches are representative techniques achieving 0D–2D quantum well, wire, and dot semiconductor III-V heterostructures with precise structural accuracy with atomic resolution. Based on the background of those epitaxial techniques, high-quality, single-crystalline III-V heterostructures have been achieved. III-V Nanowires have been proposed for the next generation of nanoscale optical and electrical devices such as nanowire light emitting diodes, lasers, photovoltaics, and transistors. Key issues for the realization of those devices involve the superior mobility and optical properties of III-V materials (i.e., nitride-, phosphide-, and arsenide-related heterostructure systems). Further, the developed epitaxial growth technique enables electronic carrier control through the formation of quantum structures and precise doping, which can be introduced into the nanowire system. The growth can extend the functions of the material systems through the introduction of elements with large miscibility gap, or, alternatively, by the formation of hybrid heterostructures between semiconductors and another material systems. This book reviews recent progresses of such novel III-V semiconductor nanowires, covering a wide range of aspects from the epitaxial growth to the device applications. Prospects of such advanced 1D structures for nanoscience and nanotechnology are also discussed.

Download or read book Henry James An Alien s History of America written by MARTHA BANTA and published by Sapienza Università Editrice. This book was released on 2016 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Martha Banta’s Henry James: An Alien’s “History” of America is the product of a lifetime of thinking about James and his odd, but oddly productive, relation to the land of his birth. A “biography” of an “autobiography,” it serves as a peripatetic history of the central cross-currents and intersections between Europe and America, memory and history, romance and realism. These diverse elements structure James’s channeling of his own experience as a displaced or “alienated” American into a variety of genres: memoirs and travel writing, novels and tales, letters and literary criticism, social and cultural commentary. Together they constitute the “never completed novel” of his ongoing “autobiographical” project. In its masterful weaving together of materials, text, and time-frames, Henry James: An Alien’s “History” of America moves fluidly back and forth over the intricate tapestry of James’s life and texts. It identifies and analyzes key moments, words, and tropes that echo across the years, tracing the instances of repetition, reversal, self-revelation, and re-vision that underwrite this “life-record.” This study represents a major advance over conventional, sometimes oversimplified readings of James’s “international theme.” His attitudes about both Europe and America emerge here in their full complexity and contradictoriness. The breadth and depth of Banta’s knowledge of James and of the historical America from which he emerged and which he never ceased to engage, however ambivalently, will make this a rich reading experience for general readers as well as scholars. David McWhirter editor of Henry James’s New York Edition: The Construction of Authorship and Henry James in Context.

Download or read book Optical Properties and Applications of Semiconductors written by Inamuddin and published by CRC Press. This book was released on 2022-07-18 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductors with optical characteristics have found widespread use in evolving semiconductor photovoltaics, where optical features are important. The industrialization of semiconductors and their allied applications have paved the way for optical measurement techniques to be used in new ways. Due to their unique properties, semiconductors are key components in the daily employed technologies in healthcare, computing, communications, green energy, and a range of other uses. This book examines the fundamental optical properties and applications of semiconductors. It summarizes the information as well as the optical characteristics and applicability of semiconductors through an in-depth review of the literature. Accomplished experts in the field share their knowledge and examine new developments. FEATURES Comprehensive coverage of all types of optical applications using semiconductors Explores relevant composite materials and devices for each application Addresses the optical properties of crystalline and amorphous semiconductors Describes new developments in the field and future potential applications Optical Properties and Applications of Semiconductors is a comprehensive reference and an invaluable resource for engineers, scientists, academics, and industry R&D teams working in applied physics.

Download or read book Semiconductor Nanowires written by J Arbiol and published by Elsevier. This book was released on 2015-03-31 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanowires promise to provide the building blocks for a new generation of nanoscale electronic and optoelectronic devices. Semiconductor Nanowires: Materials, Synthesis, Characterization and Applications covers advanced materials for nanowires, the growth and synthesis of semiconductor nanowires—including methods such as solution growth, MOVPE, MBE, and self-organization. Characterizing the properties of semiconductor nanowires is covered in chapters describing studies using TEM, SPM, and Raman scattering. Applications of semiconductor nanowires are discussed in chapters focusing on solar cells, battery electrodes, sensors, optoelectronics and biology. - Explores a selection of advanced materials for semiconductor nanowires - Outlines key techniques for the property assessment and characterization of semiconductor nanowires - Covers a broad range of applications across a number of fields

Download or read book Novel Compound Semiconductor Nanowires written by Fumitaro Ishikawa and published by CRC Press. This book was released on 2017-10-17 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: One dimensional electronic materials are expected to be key components owing to their potential applications in nanoscale electronics, optics, energy storage, and biology. Besides, compound semiconductors have been greatly developed as epitaxial growth crystal materials. Molecular beam and metalorganic vapor phase epitaxy approaches are representative techniques achieving 0D–2D quantum well, wire, and dot semiconductor III-V heterostructures with precise structural accuracy with atomic resolution. Based on the background of those epitaxial techniques, high-quality, single-crystalline III-V heterostructures have been achieved. III-V Nanowires have been proposed for the next generation of nanoscale optical and electrical devices such as nanowire light emitting diodes, lasers, photovoltaics, and transistors. Key issues for the realization of those devices involve the superior mobility and optical properties of III-V materials (i.e., nitride-, phosphide-, and arsenide-related heterostructure systems). Further, the developed epitaxial growth technique enables electronic carrier control through the formation of quantum structures and precise doping, which can be introduced into the nanowire system. The growth can extend the functions of the material systems through the introduction of elements with large miscibility gap, or, alternatively, by the formation of hybrid heterostructures between semiconductors and another material systems. This book reviews recent progresses of such novel III-V semiconductor nanowires, covering a wide range of aspects from the epitaxial growth to the device applications. Prospects of such advanced 1D structures for nanoscience and nanotechnology are also discussed.

Download or read book Nanowires written by Abbass A. Hashim and published by BoD – Books on Demand. This book was released on 2011-07-19 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding and building up the foundation of nanowire concept is a high requirement and a bridge to new technologies. Any attempt in such direction is considered as one step forward in the challenge of advanced nanotechnology. In the last few years, InTech scientific publisher has been taking the initiative of helping worldwide scientists to share and improve the methods and the nanowire technology. This book is one of InTechs attempts to contribute to the promotion of this technology.

Download or read book Magnetic Nano and Microwires written by Manuel Vázquez and published by Woodhead Publishing. This book was released on 2020-03-31 with total page 1010 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Nano-and Microwires: Design, Synthesis, Properties and Applications, Second Edition, reviews the growth and processing of nanowires and nanowire heterostructures using such methods as sol-gel and electrodeposition, focused-electron/ion-beam-induced deposition, epitaxial growth by chemical vapor transport, and more. Other sections cover engineering nanoporous anodic alumina, discuss magnetic and transport properties, domains, domain walls in nano-and microwires. and provide updates on skyrmions, domain walls, magnetism and transport, and the latest techniques to characterize and analyze these effects. Final sections cover applications, both current and emerging, and new chapters on memory, sensor, thermoelectric and nanorobotics applications. This book will be an ideal resource for academics and industry professionals working in the disciplines of materials science, physics, chemistry, electrical and electronic engineering and nanoscience.

Download or read book Advanced Composite Materials and Manufacturing Engineering written by B. Xu and published by Trans Tech Publications Ltd. This book was released on 2012-10-22 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selected, peer reviewed papers from the 2012 International Conference on Advanced Composite Materials and Manufacturing Engineering (CMME 2012), October13-14, 2012, Beijing, China

Download or read book X Ray Absorption Spectroscopy of Semiconductors written by Claudia S. Schnohr and published by Springer. This book was released on 2014-11-05 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray Absorption Spectroscopy (XAS) is a powerful technique with which to probe the properties of matter, equally applicable to the solid, liquid and gas phases. Semiconductors are arguably our most technologically-relevant group of materials given they form the basis of the electronic and photonic devices that now so widely permeate almost every aspect of our society. The most effective utilisation of these materials today and tomorrow necessitates a detailed knowledge of their structural and vibrational properties. Through a series of comprehensive reviews, this book demonstrates the versatility of XAS for semiconductor materials analysis and presents important research activities in this ever growing field. A short introduction of the technique, aimed primarily at XAS newcomers, is followed by twenty independent chapters dedicated to distinct groups of materials. Topics span dopants in crystalline semiconductors and disorder in amorphous semiconductors to alloys and nanometric material as well as in-situ measurements of the effects of temperature and pressure. Summarizing research in their respective fields, the authors highlight important experimental findings and demonstrate the capabilities and applications of the XAS technique. This book provides a comprehensive review and valuable reference guide for both XAS newcomers and experts involved in semiconductor materials research.

Download or read book Advances in Semiconductor Nanostructures written by Alexander V. Latyshev and published by Elsevier. This book was released on 2016-11-10 with total page 553 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Semiconductor Nanostructures: Growth, Characterization, Properties and Applications focuses on the physical aspects of semiconductor nanostructures, including growth and processing of semiconductor nanostructures by molecular-beam epitaxy, ion-beam implantation/synthesis, pulsed laser action on all types of III–V, IV, and II–VI semiconductors, nanofabrication by bottom-up and top-down approaches, real-time observations using in situ UHV-REM and high-resolution TEM of atomic structure of quantum well, nanowires, quantum dots, and heterostructures and their electrical, optical, magnetic, and spin phenomena. The very comprehensive nature of the book makes it an indispensable source of information for researchers, scientists, and post-graduate students in the field of semiconductor physics, condensed matter physics, and physics of nanostructures, helping them in their daily research. - Presents a comprehensive reference on the novel physical phenomena and properties of semiconductor nanostructures - Covers recent developments in the field from all over the world - Provides an International approach, as chapters are based on results obtained in collaboration with research groups from Russia, Germany, France, England, Japan, Holland, USA, Belgium, China, Israel, Brazil, and former Soviet Union countries

Download or read book Nanotubes and Nanowires written by C N Ram Rao and published by Royal Society of Chemistry. This book was released on 2007-10-31 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research and literature on nanomaterials has exploded in volume in recent years. Nanotubes (both of carbon and inorganic materials) can be made in a variety of ways, and they demonstrate a wide range of interesting properties. Many of these properties, such as high mechanical strength and interesting electronic properties relate directly to potential applications. Nanowires have been made from a vast array of inorganic materials and provide great scope for further research into their properties and possible applications. This book provides a comprehensive and up-to-date survey of the research areas of carbon nanotubes, inorganic nanotubes and nanowires including: synthesis; characterisation; properties; applications Nanotubes and Nanowires includes an extensive list of references and is ideal both for graduates needing an introduction to the field of nanomaterials as well as for professionals and researchers in academia and industry.