Download or read book Investigation of Quantum Confinement in Silicon and Germanium Semiconductor Nanocrystals and Their Application in Photonic Devices written by Gildardo Rios Delgado and published by . This book was released on 1997 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 862 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantum Confinement VI written by M. Cahay and published by The Electrochemical Society. This book was released on 2001 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This book is a collection of some of the papers presented at the Sixth International Symposium on Quantum Confinement: Nanostructures Materials and Quantum Devices held September 5-6, 2001 in San Francisco, CA, as part of the 200th Meeting of the Electrochemical Society."

Download or read book Colloidal Synthesis and Photophysical Characterization of Group IV Alloy and Group IV V Semiconductors written by Venkatesham Tallapally and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials, typically less than 100 nm size in any direction have gained noteworthy interest from scientific community owing to their significantly different and often improved physical properties compared to their bulk counterparts. Semiconductor nanoparticles (NPs) are of great interest to study their tunable optical properties, primarily as a function of size and shape. Accordingly, there has been a lot of attention paid to synthesize discrete semiconducting nanoparticles, of where Group III-V and II-VI materials have been studied extensively. In contrast, Group IV and Group IV-V based nanocrystals as earth abundant and less-non-toxic semiconductors have not been studied thoroughly. From the class of Group IV, Ge1-xSnxalloys are prime candidates for the fabrication of Si-compatible applications in the field of electronic and photonic devices, transistors, and charge storage devices. In addition, Ge1-xSnx alloys are potentials candidates for bio-sensing applications as alternative to toxic materials. Tin phosphides, a class of Group IV-V materials with their promising applications in thermoelectric, photocatalytic, and charge storage devices. However, both aforementioned semiconductors have not been studied thoroughly for their full potential in visible (Vis) to near infrared (NIR) optoelectronic applications. In this dissertation research, we have successfully developed unique synthetic strategies to produce Ge1-xSnxalloy quantum dots (QDs) and tin phosphide (Sn3P4, SnP, and Sn4P3) nanoparticles with tunable physical properties and crystal structures for potential applications in IR technologies. Low-cost, less-non-toxic, and abundantly-produced Ge1-xSnxalloys are an interesting class of narrow energy-gap semiconductors that received noteworthy interest in optical technologies. Admixing of Îł-Sn into Ge results in an indirect-to-direct bandgap crossover significantly improving light absorption and emission relative to indirect-gap Ge. However, the narrow energy-gaps reported for bulk Ge1-xSnxalloys have become a major impediment for their widespread application in optoelectronics. Herein, we report the first colloidal synthesis of Ge1-xSnxalloy quantum dots (QDs) with narrow size dispersity (3.3±0.5 -- 5.9±0.8 nm), wide range of Sn compositions (0--20.6%), and composition-tunable energy-gaps and near infrared (IR) photoluminescence (PL). The structural analysis of alloy QDs indicates linear expansion of cubic Ge lattice with increasing Sn, suggesting the formation of strain-free nanoalloys. The successful incorporation of Îł-Sn into crystalline Ge has been confirmed by electron microscopy, which suggests the homogeneous solid solution behavior of QDs. The quantum confinement effects have resulted in energy gaps that are significantly blue-shifted from bulk Ge for Ge1-xSnxalloy QDs with composition-tunable absorption onsets (1.72±0.84 eV for x=1.5--20.6%) and PL peaks (1.62--1.31 eV for x=1.5--5.6%). Time-resolved PL (TRPL) spectroscopy revealed microsecond and nanosecond timescale decays at 15 K and 295 K, respectively owing to radiative recombination of dark and bright excitons as well as the interplay of surface traps and core electronic states. Realization of low-to-non-toxic and silicon-compatible Ge1-xSnxQDs with composition-tunable near IR PL allows the unprecedented expansion of direct-gap Group IV semiconductors to a wide range of biomedical and advanced technological studies. Tin phosphides are a class of materials that received noteworthy interest in photocatalysis, charge storage and thermoelectric devices. Dual stable oxidation states of tin (Sn2+ and Sn4+) enable tin phosphides to exhibit different stoichiometries and crystal phases. However, the synthesis of such nanostructures with control over morphology and crystal structure has proven a challenging task. Herein, we report the first colloidal synthesis of size, shape, and phase controlled, narrowly disperse rhombohedral Sn4P3, hexagonal SnP, and amorphous tin phosphide nanoparticles (NPs) displaying tunable morphologies and size dependent physical properties. The control over NP morphology and crystal phase was achieved by tuning the nucleation/growth temperature, molar ratio of Sn/P, and incorporation of additional coordinating solvents (alkylphosphines). The absorption spectra of smaller NPs exhibit size-dependent blue shifts in energy gaps (0.88--1.38 eV) compared to the theoretical value of bulk Sn3P4 (0.83 eV), consistent with quantum confinement effects. The amorphous NPs adopt rhombohedral Sn4P3 and hexagonal SnP crystal structures at 180 and 250 ̊C, respectively. Structural and surface analysis indicates consistent bond energies for phosphorus across different crystal phases, whereas the rhombohedral Sn4P3 NPs demonstrate Sn oxidation states distinctive from those of the hexagonal and amorphous NPs owing to complex chemical structure. All phases exhibit N(1s) and ʋ(N-H) energies suggestive of alkylamine surface functionalization and are devoid of tetragonal Sn impurities.

Download or read book Nanostructured Semiconductors written by Petra Granitzer and published by CRC Press. This book was released on 2014-03-11 with total page 694 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on nanostructured semiconductors, their fabrication, and their application in various fields such as optics, acoustics, and biomedicine. It presents a compendium of recent developments in nanostructured and hybrid materials and also contains a collection of principles and approaches related to nano-size semiconductors. The text su

Download or read book Quantum Confinement Carrier Dynamics and Interfacial Processes in Nanostructured Direct written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The behavior of semiconductor clusters precipitated in an insulated matrix was investigated. Semiconductor compositions of CdTe, Si and Ge were studies and the insulating matrix was amorphous SiO2. As a function of size, quantum confinement effects were observed in all three composite systems. However significant differences were observed between the direct-gap column 2-6 semiconductors and the indirect-gap column 4 semiconductors. As observed by others, the direct-gap 2-6 semiconductors showed a distinct saturation in the energy-gap blue shift with decreasing size. Theoretical studies using a 20-band k dot p calculation of the electronic and valence bands for a 3-dimensionally confined CdTe semiconductor showed that mixing of the conduction band states leads to a flattening of the central valley. This increases the electron mass drastically and saturates the size dependent blue shift in the bandgap. In contrast, the blue shift in the Si and Ge nanocrystals showed no sign of saturation and increased drastically with decreasing size. In fact, Si and Ge crystals were formed with blue shift values that moved the bandgap to the near UV region. We examined the absorption curves to determine whether the bandgap was direct or indirect in the quantum dots. The results are that the absorption shows an indirect gap for all but the smallest Si crystals and an indirect gap for all Ge crystals. Raman studies showed negligible size dependence due to a lack of phonon confinement in the matrix embedded clusters. Exciton saturation and recovery times were found to be very short (of the order of 400fs) and are the fastest reported for any quantum dot system. Work to examine the type of confinement obtained in a matrix that consists of a transparent conductor is under way. Studies of the photoinduced absorption change in GeSe glasses showed a significant effect of photodarkening, regardless of composition. The photodarkening effect appears to be composed of permanent and transient effects, presumed to be associated with photo-induced structural changes in the glass. The transient effects appear to have recovery times in at least two different time scales--one in minutes and one in less than a microsecond. Time-resolved studies are under way to determine the structural origin of each photodarkening effect.

Download or read book Development of Silicon Germanium based Quantum Dots for Nanoelectronic Device Applications written by Sandro John Di Giacomo and published by . This book was released on 2005 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: As CMOS dimensions decrease each year, the International Technology Roadmap for Semiconductors (ITRS) encourages development of "emerging research devices" to eventually replace CMOS. SiGe-based quantum dots, the focus of this study, are attractive because they can be integrated with existing Si -based devices and fabricated using existing processes. This process exploits self-limiting effects in Si nanopillar oxidation and Ge segregation during SiGe oxidation to fabricate uniformly sized Ge quantum dots suitable for room temperature operation. In this study, four fabrication processes were investigated: electron-beam lithography (EBL), inductively-coupled plasma (ICP) etching, thermal oxidation, and transmission electron microscopy (TEM). The samples consisted of rows of closely spaced Si nanopillars, with diameters of 25-100 nm and heights of 80-600 nm.

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.

Download or read book Handbook of Self Assembled Semiconductor Nanostructures for Novel Devices in Photonics and Electronics written by Mohamed Henini and published by Elsevier Science. This book was released on 2008 with total page 841 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1969, Leo Esaki (1973 Nobel Laureate) and Ray Tsu from IBM, USA, proposed research on “man-made crystals” using a semiconductor superlattice (a semiconductor structure comprising several alternating ultra-thin layers of semiconductor materials with different properties). This invention was perhaps the first proposal to advocate the engineering of a new semiconductor material, and triggered a wide spectrum of experimental and theoretical investigations. However, the study of what are now called low dimensional structures (LDS) began in the late 1970's when sufficiently thin epitaxial layers were first produced following developments in the technology of epitaxial growth of semiconductors, mainly pioneered in industrial laboratories for device purposes. The LDS are materials structures whose dimensions are comparable with inter-atomic distances in solids (i.e. nanometre, nm). Their electronic properties are significantly different from the same material in bulk form. These properties are changed by quantum effects. At the inception of their investigation it was already clear that such structures were of great scientific interest and excitement and their novel properties caused by quantum effects offered potential for application in new devices. Moreover these complex LDS offer device engineers new design opportunities for tailor-made new generation electronic devices. The LDS could be considered as a new branch of condensed matter physics because of the large variety of possible structures and the changes in the physical processes. One of the promising fabrication methods to produce and study structures with a dimension less than two such as quantum wires and quantum dots, in order to realise novel devices that make use of low-dimensional confinement effects, is self-organisation. Self-assembled nanostructured materials offer a number of advantages over conventional material technologies in a wide-range of sectors. Clearly, future research work on self-assembled nanostructures will connect diverse areas of material science, physics, chemistry, electronics and optoelectronics. Key Features: - Contributors are world leaders in the field - Brings together all the factors which are essential in self-organisation of quantum nanostructures - Reviews the current status of research and development in self-organised nanostructured materials - Provides a ready source of information on a wide range of topics - Useful to any scientist who is involved in nanotechnology - Excellent starting point for workers entering the field - Serves as an excellent reference manual

Download or read book 21st Century Nanoscience written by Klaus D. Sattler and published by CRC Press. This book was released on 2022-01-18 with total page 4153 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 21st Century Nanoscience Handbook will be the most comprehensive, up-to-date large reference work for the field of nanoscience. Handbook of Nanophysics, by the same editor, published in the fall of 2010, was embraced as the first comprehensive reference to consider both fundamental and applied aspects of nanophysics. This follow-up project has been conceived as a necessary expansion and full update that considers the significant advances made in the field since 2010. It goes well beyond the physics as warranted by recent developments in the field. Key Features: Provides the most comprehensive, up-to-date large reference work for the field. Chapters written by international experts in the field. Emphasises presentation and real results and applications. This handbook distinguishes itself from other works by its breadth of coverage, readability and timely topics. The intended readership is very broad, from students and instructors to engineers, physicists, chemists, biologists, biomedical researchers, industry professionals, governmental scientists, and others whose work is impacted by nanotechnology. It will be an indispensable resource in academic, government, and industry libraries worldwide. The fields impacted by nanoscience extend from materials science and engineering to biotechnology, biomedical engineering, medicine, electrical engineering, pharmaceutical science, computer technology, aerospace engineering, mechanical engineering, food science, and beyond.

Download or read book Photonic Materials Devices and Applications II written by Ali Serpengüzel and published by SPIE-International Society for Optical Engineering. This book was released on 2007 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of SPIE present the original research papers presented at SPIE conferences and other high-quality conferences in the broad-ranging fields of optics and photonics. These books provide prompt access to the latest innovations in research and technology in their respective fields. Proceedings of SPIE are among the most cited references in patent literature.

Download or read book Altering Quantum Confinement in Semiconductor Nanocrystals Using Strongly Interacting Exciton delocalizing Ligands written by Michael Steven Azzaro and published by . This book was released on 2019 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Semiconductor nanocrystals have long been studied as alternatives to traditional bulk semiconductor materials as active components in optoelectronic devices due to their size-tunable absorption and emission properties, as well as their ability to be processed into thin films from colloidal solutions. However, creating highly conductive nanocrystal solids remains a substantial challenge due to the presence of long (~2-3 nm), insulating “native ligands” that are used to terminate nanocrystal growth and provide colloidal stability following their synthesis. In this work we have used a variety of structural and spectroscopic characterization to investigate the chemical and physical changes associated with exchanging these native ligands for ligands that have the proper energetics and orbital symmetry conditions to interact strongly with nanocrystal electronic states, termed “exciton-delocalizing ligands”. This interaction is proposed to allow for delocalization of carriers beyond the nanocrystal core and into the ligand shell by reducing the potential energy barrier at the nanocrystal-ligand interface, which can be used to improve transport properties in nanocrystal solids. Colloidal nanocrystal samples were investigated to determine if this strong interaction impacts carrier cooling rates, as this would provide insight into the degree of mixed nanocrystal-ligand character of these states. Using transient absorption spectroscopy we measured the change in electron and hole cooling rates following ligand exchange with the exciton-delocalizing ligand phenyldithiocarbamate and found that when excited near the nanocrystal band edge, the valence band states of the nanocrystals interact more strongly with the ligand than those in the conduction band. Solid-state ligand exchange with phenyldithiocarbamate was then carried out on nanocrystal films to determine if the strong nanocrystal-ligand interaction of these exciton-delocalizing ligands impacts the exciton mobility in nanocrystal solids. Using a combination of transient absorption spectroscopy and kinetic Monte-Carlo simulations we have found that treatment with phenyldithiocarbamate yields a drastic increase in the diffusivity of excitons in nanocrystal films, and this improved transport occurs via a unique tunneling-type mechanism rather than more traditional Förster Resonance Energy Transfer. A combination of multidimensional spectroscopy and transient absorption were used to probe the electronic structure and dynamics of ligand-exchanged nanocrystals in both solution and films. Contributions to homogeneous broadening are assigned as primarily due to ligand fluctuations in solution and energy transfer between NCs in solids. Finally, by varying the initial excitation energy in the nanocrystal we find that more highly excited carriers exhibit a greater degree of delocalization resulting from a greater degree of mixed nanocrystal-ligand character of these states

Download or read book 21st Century Nanoscience A Handbook written by Klaus D. Sattler and published by CRC Press. This book was released on 2019-11-26 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: This up-to-date reference is the most comprehensive summary of the field of nanoscience and its applications. It begins with fundamental properties at the nanoscale and then goes well beyond into the practical aspects of the design, synthesis, and use of nanomaterials in various industries. It emphasizes the vast strides made in the field over the past decade – the chapters focus on new, promising directions as well as emerging theoretical and experimental methods. The contents incorporate experimental data and graphs where appropriate, as well as supporting tables and figures with a tutorial approach.

Download or read book Proceedings of the Fourth International Symposium on Quantum Confinement written by M. Cahay and published by The Electrochemical Society. This book was released on 1997 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantum Confinement Carrier Dynamics and Interfacial Processes in Nanostructured Direct indirect gap Semiconductor glass Composites written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The behavior of semiconductor clusters precipitated in an insulated matrix was investigated. Semiconductor compositions of CdTe, Si and Ge were studies and the insulating matrix was amorphous SiO[sub 2]. As a function of size, quantum confinement effects were observed in all three composite systems. However significant differences were observed between the direct-gap column 2-6 semiconductors and the indirect-gap column 4 semiconductors. As observed by others, the direct-gap 2-6 semiconductors showed a distinct saturation in the energy-gap blue shift with decreasing size. Theoretical studies using a 20-band k dot p calculation of the electronic and valence bands for a 3-dimensionally confined CdTe semiconductor showed that mixing of the conduction band states leads to a flattening of the central valley. This increases the electron mass drastically and saturates the size dependent blue shift in the bandgap. In contrast, the blue shift in the Si and Ge nanocrystals showed no sign of saturation and increased drastically with decreasing size. In fact, Si and Ge crystals were formed with blue shift values that moved the bandgap to the near UV region. We examined the absorption curves to determine whether the bandgap was direct or indirect in the quantum dots. The results are that the absorption shows an indirect gap for all but the smallest Si crystals and an indirect gap for all Ge crystals. Raman studies showed negligible size dependence due to a lack of phonon confinement in the matrix embedded clusters. Exciton saturation and recovery times were found to be very short (of the order of 400fs) and are the fastest reported for any quantum dot system. Work to examine the type of confinement obtained in a matrix that consists of a transparent conductor is under way. Studies of the photoinduced absorption change in GeSe glasses showed a significant effect of photodarkening, regardless of composition. The photodarkening effect appears to be composed of permanent and transient effects, presumed to be associated with photo-induced structural changes in the glass. The transient effects appear to have recovery times in at least two different time scales--one in minutes and one in less than a microsecond. Time-resolved studies are under way to determine the structural origin of each photodarkening effect.

Download or read book Electronic Structure of Germanium Nanocrystal Films Probed with Synchrotron Radiation written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The fundamental structure--property relationship of semiconductor quantum dots has been investigated. For deposited germanium nanocrystals strong quantum confinement effects have been determined with synchrotron radiation based x-ray absorption and photoemission techniques. The nanocrystals are condensed out of the gas phase with a narrow size distribution and subsequently deposited in situ onto various substrates. The particles are crystalline in the cubic phase with a structurally disordered surface shell and the resulting film morphology depends strongly on the substrate material and condition. The disordered surface region has an impact on the overall electronic structure of the particles. In a size-dependent study, the conduction and valence band edge of germanium nanocrystals have been measured for the first time and compared to the bulk crystal. The band edges move to higher energies as the particle size is decreased, consistent with quantum confinement theory. To obtain a more accurate analysis of confinement effects in the empty states, a novel analysis method utilizing an effective particle size for the x-ray absorption experiment, which allows a deconvolution of absorption edge broadening effects, has been introduced. Comparison of the present study to earlier studies on silicon reveals that germanium exhibits stronger quantum confinement effects than silicon. Below a critical particle size of 2.3 " 0.7 nm, the band gap of germanium becomes larger than that of silicon--even if it is the opposite for bulk materials. This result agrees phenomenologically with effective mass and tight binding theories but contradicts the findings of recent pseudopotential calculations. The discrepancy between theory and experiments is attributed to the differences in the theoretical models and experimental systems. The experimentally observed structural disorder of the particle surface has to be included in the theoretical models.

Download or read book Colloidal Quantum Dot Optoelectronics and Photovoltaics written by Gerasimos Konstantatos and published by Cambridge University Press. This book was released on 2013-11-07 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Captures the most up-to-date research in the field, written in an accessible style by the world's leading experts.