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Author: Supriyo Bandyopadhyay Publisher: ISBN: Category : Science Languages : en Pages : 458
Book Description
Quantum Dots and Nanowires provides coverage on various emerging aspects of quantum dots and nanowires. This book covers recent advances in physical and chemical synthetic approaches, processing and fabrication of semiconductor quantum-dot arrays, superlattices, self-assemblies, nanowires, nanotubes and nanobelts, computational modeling approaches, spectroscopic characterization, their unique electrical, optical, magnetic and physical properties associated with size effect, transport phenomena, quantum computing, and other potential applications.
Author: Supriyo Bandyopadhyay Publisher: ISBN: Category : Science Languages : en Pages : 458
Book Description
Quantum Dots and Nanowires provides coverage on various emerging aspects of quantum dots and nanowires. This book covers recent advances in physical and chemical synthetic approaches, processing and fabrication of semiconductor quantum-dot arrays, superlattices, self-assemblies, nanowires, nanotubes and nanobelts, computational modeling approaches, spectroscopic characterization, their unique electrical, optical, magnetic and physical properties associated with size effect, transport phenomena, quantum computing, and other potential applications.
Author: P. Guyot-Sionnest Publisher: ISBN: Category : Science Languages : en Pages : 456
Book Description
Nanostructures of semiconductors and metals show novel optical and transport properties, and offer the perspective of designing materials properties with unprecedented flexibility and control. This has motivated research in the synthesis and characterization of new materials. This 2004 book brings together scientists with various levels of expertise in the growth, characterization and applications of inorganic nanostructures, such as quantum dots, nanowires and nanorods, to discuss and share developments in the field. Reports focus on techniques to prepare and characterize novel materials, investigations of novel optical and electronic properties, and novel applications, such as those that are biologically inspired. Topics include: synthesis and characterization of semiconductor quantum dots, nanoparticles and nanowires using wet chemistry and molecular beam approaches; synthesis, characterization and novel properties of metallic nanostructures; optical properties of neutral and charged excitons and exciton complexes in self-assembled quantum dots; nanoscale devices and sensors based on nanostructures and their properties; and design and characterization of quantum dot-bioconjugates and their use in assay developments.
Author: Alexander Tartakovskii Publisher: Cambridge University Press ISBN: 1107012589 Category : Science Languages : en Pages : 377
Book Description
A comprehensive review of cutting-edge solid state research, focusing on quantum dot nanostructures, for graduate students and researchers.
Author: Klaus D. Sattler Publisher: CRC Press ISBN: 1420075438 Category : Science Languages : en Pages : 770
Book Description
Intensive research on fullerenes, nanoparticles, and quantum dots in the 1990s led to interest in nanotubes and nanowires in subsequent years. Handbook of Nanophysics: Nanotubes and Nanowires focuses on the fundamental physics and latest applications of these important nanoscale materials and structures. Each peer-reviewed chapter contains a broad-
Author: Zhiming M Wang Publisher: Springer Science & Business Media ISBN: 0387741917 Category : Technology & Engineering Languages : en Pages : 470
Book Description
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.
Author: Mattias Jansson Publisher: Linköping University Electronic Press ISBN: 9179298834 Category : Electronic books Languages : en Pages : 77
Book Description
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.
Author: Victor I. Klimov Publisher: CRC Press ISBN: 1420079271 Category : Technology & Engineering Languages : en Pages : 485
Book Description
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.
Author: Klaus D. Sattler Publisher: CRC Press ISBN: 1420075454 Category : Science Languages : en Pages : 718
Book Description
In the 1990s, nanoparticles and quantum dots began to be used in optical, electronic, and biological applications. Now they are being studied for use in solid-state quantum computation, tumor imaging, and photovoltaics. Handbook of Nanophysics: Nanoparticles and Quantum Dots focuses on the fundamental physics of these nanoscale materials and struct
Author: Alexandre S. Alexandrov Publisher: Springer Science & Business Media ISBN: 1402020937 Category : Technology & Engineering Languages : en Pages : 434
Book Description
There is a growing understanding that the progress of the conventional silicon technology will reach its physical, engineering and economic limits in near future. This fact, however, does not mean that progress in computing will slow down. What will take us beyond the silicon era are new nano-technologies that are being pursued in university and corporate laboratories around the world. In particular, molecular switching devices and systems that will self-assemble through molecular recognition are being designed and studied. Many labora tories are now testing new types of these and other reversible switches, as well as fabricating nanowires needed to connect circuit elements together. But there are still significant opportunities and demand for invention and discovery be fore nanoelectronics will become a reality. The actual mechanisms of transport through molecular quantum dots and nanowires are of the highest current ex perimental and theoretical interest. In particular, there is growing evidence that both electron-vibron interactions and electron-electron correlations are impor tant. Further progress requires worldwide efforts of trans-disciplinary teams of physicists, quantum chemists, material and computer scientists, and engineers.
Author: Supriyo Bandyopadhyay
Author: Supriyo Bandyopadhyay
Author: P. Guyot-Sionnest
Author: Alexander Tartakovskii
Author: Klaus D. Sattler
Author: Zhiming M Wang
Author: Mattias Jansson
Author: Victor I. Klimov
Author: Klaus D. Sattler
Author: Alexandre S. Alexandrov
Author: Gerasimos Konstantatos