Download or read book Electronic Optical and Thermal Properties of Reduced dimensional Semiconductors written by Shouting Huang and published by . This book was released on 2013 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reduced-dimensional materials have attracted tremendous attention because of their new physics and exotic properties, which are of great interests for fundamental science. More importantly, the manipulation and engineering of matter on an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary but unreliable parameters extracted from previously-studied bulk materials. In this sense, quantitative, parameter-free approaches are highly useful for understanding properties of reduced-dimensional materials and, furthermore, predicting their novel applications. The first-principles density functional theory (DFT) is proven to be a reliable and convenient tool. In particular, recent progress in many-body perturbation theory (MBPT) makes it possible to calculate excited-state properties, e.g., quasiparticle (QP) band gap and optical excitations, by the first-principles approach based on DFT. Therefore, during my PhD study, I employed first-principles calculations based on DFT and MBPT to systematically study fundamental properties of typical reduced-dimensional semiconductors, i.e., the electronic structure, phonons, and optical excitations of core-shell nanowires (NWs) and graphene-like two-dimensional (2D) structures of current interests. First, I present first-principles studies on how to engineer band alignments of nano-sized radial heterojunctions, Si/Ge core-shell NWs. Our calculation reveals that band offsets in these one-dimensional (1D) nanostructures can be tailored by applying axial strain or varying core-shell sizes. In particular, the valence band offset can be efficiently tuned across a wide range and even be diminished via applied strain. Two mechanisms contribute to this tuning of band offsets. Furthermore, varying the size of Si/Ge core-shell NWs and corresponding quantum confinement is shown to be efficient for modifying both valence and conduction band offsets simultaneously. Our proposed approaches to control band offsets in nano-sized heterojunctions may be of practical interest for nanoelectronic and photovoltaic applications. Additionally, I also studied the lattice vibrational modes of Si/Ge core-shell NWs. Our calculations show that the internal strain induced by the lattice mismatch between core and shell plays an important role in significantly shifting the frequency of characteristic optical modes of core-shell NWs. In particular, our simulation demonstrates that these frequency shifts can be detected by Raman-scattering experiments, giving rise to a convenient and nondestructive way to obtain structural information of core-shell materials. Meanwhile, another type of collective modes, the radial breathing modes (RBM), is identified in Si-core/Ge-shell NWs and their frequency dependence is explained by an elastic media model. Our studied vibrational modes and their frequency evolution are useful for thermoelectric applications based on core-shell nanostructures. Then I studied optical properties and exciton spectra of 2D semiconducting carbon structures. The energy spectra and wavefunctions of excitons in the 2D graphene derivatives, i.e., graphyne and graphane, are found to be strongly modified by quantum confinement, making them qualitatively different from the usual Rydberg series. However, their parity and optical selection rules are preserved. Thus a one-parameter hydrogenic model is applied to quantitatively explain the ab initio exciton spectra, and allows one to extrapolate the electron-hole binding energy from optical spectroscopies of 2D semiconductors without costly simulations. Meanwhile, our calculated optical absorption spectrum and enhanced spin singlet-triplet splitting project graphyne, an allotrope of graphene, as a good candidate for intriguing energy and biomedical applications. Lastly, we report first-principles results on electronic structures of 2D graphenelike system, i.e., silicene. For planar and simply buckled silicene structures, we confirm their zero-gap nature and show a significant renormalization of their Fermi velocity ix by including many-electron effects. However, the other two recently proposed silicene structures exhibit a finite band gap, indicating that they are gapped semiconductors instead of expected Dirac-fermion semimetals. This finite band gap of the latter two structures is preserved even with the Ag substrate included. The gap opening is explained by the symmetry breaking of the buckled structures. Moreover, our GW calculation reveals enhanced many-electron effects in these 2D structures. Finally the band gap of the latter two structures can be tuned in a wide range by applying strain.

Download or read book Strain Tuning of Thermal Electrical and Optical Properties of Semiconductors written by Xianghai Meng and published by . This book was released on 2019 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery of graphene by mechanical exfoliation has opened a new realm of research. Compared to traditional 3D crystal structures, 2D materials are characterized by strong in-plane covalent bond and weak interlayer van der Waals force, giving them unique 2D crystal structure. In the past ten years, various 2D materials have been explored with very different electronic properties, ranging from wide band-gap insulators to conductors. Owing to the different bond strength, 2D materials behave differently in their electrical, thermal properties along the cross-plane and in-plane direction. In addition, the in-plane electrical, optical and thermal properties are also found to be anisotropic for some particular 2D materials due to the asymmetric crystal structure. Both the in-plane and cross-plane anisotropic properties of 2D materials give rise to a possibility to design the micro/nano devices in various applications. The intrinsic properties of TMDs can be further adjusted by external factors, such as electrical fields, temperature, magnetic field, et al. Among all the external stimulations, strain has been shown an effective method to control the electronic, thermal, optical properties of semiconductors. With the discovery of 2D materials, the application of strain tuning has been growing since the reduced dimensional structures can sustain much larger strains than bulk crystals. In this dissertation, in-plane anisotropic nonlinear optical nonlinearity is studies with an Intensity-scan spectroscopy at ambient conditions. Then a diamond anvil cell (DAC) device is employed to generate large strain on MoS2. With our home-built pico-second Transient Thermoreflectance technique, ~7x enhancement in cross-plane is observed due to the pressure/strain modified interlayer interaction. Moreover, photoluminescence and Raman spectroscopy are used to probe the impurity levels in BAs crystal. Pressure/Strain modified impurity level change will also have significant effect on this high thermal conductivity material. Lastly, a modified pico-second Transient Thermoreflectance system is developed to achieve simultaneous measurement on thermal conductivity and specific heat of materials

Download or read book Growth and Optical Properties of Wide Gap II VI Low Dimensional Semiconductors written by T.C. McGill and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the Proceedings of the NATO Advanced Research Workshop on "Growth and Optical Properties of Wide Gap II-VI Low Dimensional Semiconductors", held from 2 - 6 August 1988 in Regensburg, Federal Republic of Germany, under the auspices of the NATO International Scientific Exchange Programme. Semiconducting compounds formed by combining an element from column II of the periodic table with an element from column VI (so called II-VI Semiconductors) have long promised many optoelectronic devices operating in the visible region of the spectrum. However, these materials have encountered numerous problems including: large number of defects and difficulties in obtaining p- and n-type doping. Advances in new methods of material preparation may hold the key to unlocking the unfulfilled promises. During the workshop a full session was taken up covering the prospects for wide-gap II-VI Semiconductor devices, particularly light emitting ones. The growth of bulk materials was reviewed with the view of considering II-VI substrates for the novel epitaxial techniques such as MOCVD, MBE, ALE, MOMBE and ALE-MBE. The controlled introduction of impurities during non-equilibrium growth to provide control of the doping type and conductivity was emphasized.

Download or read book Optical Properties Of Low dimensional Materials written by Yoshihiko Kanemitsu and published by World Scientific. This book was released on 1996-01-18 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book surveys recent experimental and theoretical studies on optical properties of low-dimensional materials, e.g., artificial crystals in zeolites, C60 and its related compounds, silicon nanostructures including porous Si, II-VI and III-V semiconductor quantum structures, and Pb-based natural quantum-well systems. The eight excellent detailed review articles are written by authorities on each field in Japan. All the materials introduced in this book yield new optical phenomena originating from their mesoscopic and low-dimensional characters contributing to a new research field of condensed matter and optical physics.

Download or read book Advanced Electronic Technologies and Systems Based on Low Dimensional Quantum Devices written by M. Balkanski and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume on Advanced Electronic Technologies and Systems based on Low Dimensional Quantum Devices closes a three years series of NATO -AS!' s. The first year was focused on the fundamental properties and applications. The second year was devoted to Devices Based on Low-Dimensional Semiconductor Structures. The third year is covering Systems Based on Low-Dimensional Quantum Semiconductor Devices. The three volumes containing the lectures given at the three successive NATO -ASI's constitute a complete review on the latest advances in semiconductor Science and Technology from the methods of fabrication of the quantum structures through the fundamental physics am basic knowledge of properties and projection of performances to the technology of devices and systems. In the first volume: " Fabrication, Properties and Application of Low Dimensional Semiconductors" are described the practical ways in which quantum structures are produced, the present status of the technology, difficulties encountered, and advances to be expected. The basic theory of Quantum Wells, Double Quantum Wells and Superlattices is introduced and the fundamental aspects of their optical properties are presented. The effect of reduction of dimensionality on lattice dynamics of quantum structures is also discussed. In the second volume: " Devices Based on Low Dimensional Structures" the fundamentals of quantum structures and devices in the two major fields: Electro-Optical Devices and Pseudomorphic High Eectron Mobility Transistors are extensively discussed.

Download or read book Handbook of Nitride Semiconductors and Devices Electronic and Optical Processes in Nitrides written by Hadis Morkoç and published by John Wiley & Sons. This book was released on 2009-07-30 with total page 883 pages. Available in PDF, EPUB and Kindle. Book excerpt: The three volumes of this handbook treat the fundamentals, technology and nanotechnology of nitride semiconductors with an extraordinary clarity and depth. They present all the necessary basics of semiconductor and device physics and engineering together with an extensive reference section. Volume 2 addresses the electrical and optical properties of nitride materials. It includes semiconductor metal contacts, impurity and carrier concentrations, and carrier transport in semiconductors.

Download or read book Optical Properties of III V Semiconductors written by Heinz Kalt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph is concerned with the III-V bulk and low-dimensional semiconductors, with the emphasis on the implications of multi-valley bandstructures for the physical mechanisms essential for opto-electronic devices. The optical response of such semiconductor materials is determined by many-body effects such as screening, gap narrowing, Fermi-edge singularity, electron-hole plasma and liquid formation. Consequently, the discussion of these features reflects such interdependencies with the dynamics of excitons and carriers resulting from intervalley coupling.

Download or read book The Physics of Low dimensional Semiconductors written by John H. Davies and published by Cambridge University Press. This book was released on 1998 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: The composition of modern semiconductor heterostructures can be controlled precisely on the atomic scale to create low-dimensional systems. These systems have revolutionised semiconductor physics, and their impact on technology, particularly for semiconductor lasers and ultrafast transistors, is widespread and burgeoning. This book provides an introduction to the general principles that underlie low-dimensional semiconductors. As far as possible, simple physical explanations are used, with reference to examples from actual devices. The author shows how, beginning with fundamental results from quantum mechanics and solid-state physics, a formalism can be developed that describes the properties of low-dimensional semiconductor systems. Among numerous examples, two key systems are studied in detail: the two-dimensional electron gas, employed in field-effect transistors, and the quantum well, whose optical properties find application in lasers and other opto-electronic devices. The book includes many exercises and will be invaluable to undergraduate and first-year graduate physics or electrical engineering students taking courses in low-dimensional systems or heterostructure device physics.

Download or read book Optical Properties of Semiconductors written by G. Martinez and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is widely recognized that an understanding of the optical pro perties of matter will give a great deal of important information re levant to the fundamental physical properties. This is especially true in semiconductor physics for which, due to the intrinsic low screening of these materials, the optical response is quite rich. Their spectra reflect indeed as well electronic as spin or phonon transitions. This is also in the semiconductor field that artificial structures have been recently developed, showing for the first time specific physical properties related to the low dimentionality of the electronic and vi bronic properties : with this respect the quantum and fractional quan tum Hall effects are among the most well known aspects. The associated reduced screening is also a clear manifestation of these aspects and as such favors new optical properties or at least significantly enhan ces some of them. For all these reasons, it appeared necessary to try to review in a global way what the optical investigation has brought today about the understanding of the physics of semiconductors. This volume collects the papers presented at the NATO Advanced study Inst i tut e on "Optical Properties of Semiconductors" held at the Ettore Majorana Centre, Erice, Sicily on March 9th to 20th, 1992. This school brought together 70 scientists active in research related to optical properties of semiconductors. There were 12 lecturers who pro vided the main contributions .

Download or read book Low dimensional Semiconductors written by M. J. Kelly and published by Clarendon Press. This book was released on 1995-11-23 with total page 569 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text is a first attempt to pull together the whole of semiconductor science and technology since 1970 in so far as semiconductor multilayers are concerned. Material, technology, physics and device issues are described with approximately equal emphasis, and form a single coherant point of view. The subject matter is the concern of over half of today's active semiconductor scientists and technologists, the remainder working on bulk semiconductors and devices. It is now routine to design and the prepare semiconductor multilayers at a time, with independent control over the dropping and composition in each layer. In turn these multilayers can be patterned with features that as a small as a few atomic layers in lateral extent. The resulting structures open up many new ares of exciting solid state and quantum physics. They have also led to whole new generations of electronic and optoelectronic devices whose superior performance relates back to the multilayer structures. The principles established in the field have several decades to go, advancing towards the ultimate of materials engineering, the design and preparation of solids atom by atom. The book should appeal equally to physicists, electronic engineers and materials scientists.

Download or read book Optical Properties of Narrow Gap Low Dimensional Structures written by Clivia M. Sotomayor Torres and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the Proceedings of the NATO Advanced Research Workshop on "Optical Properties of Narrow-Gap Low-Dimensional Structures", held from July 29th to August 1st, 1986, in St. Andrews, Scotland, under the auspices of the NATO International Scientific Exchange Program. The workshop was not limited to optical properties of narrow-gap semiconductor structures (Part III). Sessions on, for example, the growth methods and characterization of III-V, II-VI, and IV-VI materials, discussed in Part II, were an integral part of the workshop. Considering the small masses of the carriers in narrow-gap low dimensional structures (LOS), in Part I the enhanced band mixing and magnetic field effects are explored in the context of the envelope function approximation. Optical nonlinearities and energy relaxation phenomena applied to the well-known systems of HgCdTe and GaAs/GaAIAs, respectively, are reviewed with comments on their extension to narrow gap LOS. The relevance of optical observations in quantum transport studies is illustrated in Part IV. A review of devices based on epitaxial narrow-gap materials defines a frame of reference for future ones based on two-dimensional narrow-gap semiconductors; in addition, an analysis of the physics of quantum well lasers provides a guide to relevant parameters for narrow-gap laser devices for the infrared (Part V). The roles and potentials of special techniques are explored in Part VI, with emphasis on hydrostatic pressure techniques, since this has a pronounced effect in small-mass, narrow-gap, non-parabolic structures.

Download or read book Fabrication Properties and Applications of Low Dimensional Semiconductors written by M. Balkanski and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: A recent major development in high technology, and one which bears considerable industrial potential, is the advent of low-dimensional semiconductor quantum structures. The research and development activity in this field is moving fast and it is thus important to afford scientists and engineers the opportunity to get updated by the best experts in the field. The present book draws together the latest developments in the fabrication technology of quantum structures, as well as a competent and extensive review of their fundamental properties and some remarkable applications. The book is based on a set of lectures that introduce different aspects of the basic knowledge available, it has a tutorial content and could be used as a textbook. Each aspect is reviewed, from elementary concepts up to the latest developments. Audience: Undergraduates and graduates in electrical engineering and physics schools. Also for active scientists and engineers, updating their knowledge and understanding of the frontiers of the technology.

Download or read book Low Dimensional Semiconductor Structures written by Hilmi Ünlü and published by Springer Science & Business Media. This book was released on 2012-09-14 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting with the first transistor in 1949, the world has experienced a technological revolution which has permeated most aspects of modern life, particularly over the last generation. Yet another such revolution looms up before us with the newly developed capability to control matter on the nanometer scale. A truly extraordinary research effort, by scientists, engineers, technologists of all disciplines, in nations large and small throughout the world, is directed and vigorously pressed to develop a full understanding of the properties of matter at the nanoscale and its possible applications, to bring to fruition the promise of nanostructures to introduce a new generation of electronic and optical devices. The physics of low dimensional semiconductor structures, including heterostructures, superlattices, quantum wells, wires and dots is reviewed and their modeling is discussed in detail. The truly exceptional material, Graphene, is reviewed; its functionalization and Van der Waals interactions are included here. Recent research on optical studies of quantum dots and on the physical properties of one-dimensional quantum wires is also reported. Chapters on fabrication of nanowire – based nanogap devices by the dielectrophoretic assembly approach. The broad spectrum of research reported here incorporates chapters on nanoengineering and nanophysics. In its presentation of tutorial chapters as well as advanced research on nanostructures, this book is ideally suited to meet the needs of newcomers to the field as well as experienced researchers interested in viewing colleagues’ recent advances.

Download or read book Optical and Electro Optical Properties of Two Dimensional Semiconductors written by Carlos Gutierrez Garcia and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-dimensional (2D) materials have recently caught much attention due to their exceptional properties and their potential applications in opto-electronics. Graphene, transition metal dichalcogenides (TMDs), and black phosphorus (b-P) are some of the main candidates from the 2D material family that show great promise in their ability to have properties such as high mobility, anisotropy, desirable band gap, and many more. Here, we'll discuss some of the history of these 2D semiconductors and some of the properties that make them unique and interesting. This will be focusing on the electrical and opto-electrical properties of 2D semiconductors in measurements conducted during my graduate research studies. Some of these measurements include 2-terminal and 4-terminal contact configurations, photoconductivity, transport, photoluminescence, and Raman spectroscopy. The 2D semiconductors used in these experiments are post-graphene such as TMDs, post transition metals, and b-P. The photoconductivity was measured on few-layered WSe$_{2}$ field-effect transistors (FETs) using both 2-terminal and 4-terminal configurations under 532~nm laser source. For an incident laser power of 248 nW, we extracted 18 A/W and $\sim$4000\% for the two-terminal responsivity (R) and an external quantum efficiency (EQE) respectively, when a bias voltage $V_{ds}$ = 1 V and a gate voltage $V_{bg}$ = 10 V were applied to the sample. R and EQE saw an increase by 370\% to $\sim$85 A/W and $\sim$20000\% respectively, when using a four-terminal configuration. The photogating effect was observed in our few-layered (3-4 layers) ReS$_{2}$ FETs in which varying the incident optical power shifted the FETs' threshold voltage. The photogating effect produced a significant gain in the electrical response of the FETs to incident light as measured by R and EQE. We obtained a maximum R of 45 A/W corresponding to an EQE of $\sim$10500\% in a 4-terminal measurement of the photoconductivity in the ON-state. We attribute both the photogating and the observed gain to the influence of charge traps. We also presented a detailed study on the Raman spectra and on the temperature dependence of the electrical transport properties of arsenic-doped black phosphorus (b-AsP) with an As fraction of x = 0.25. Field-effect transistors fabricated from few-layered b-AsP exfoliated onto Si/SiO$_{2}$ substrates exhibited hole-doped like conduction with a room temperature ON/OFF current ratio of $\sim$10$^{3}$ and an intrinsic field-effect mobility approaching $\sim$300 cm$^{2}$V$^{-1}$s$^{-1}$ at 300 K which increases up to 600 cm$^{2}$V$^{-1}$s$^{-1}$ at 100 K when measured via a 4-terminal method. The ON to OFF current ratio is observed to increase up to 10$^{5}$ at 4 K. Similarly to pristine b-P, its transport properties revealed a high anisotropy between armchair and zig-zag directions. Photoluminescence (PL) and transport measurements were conducted on vanadium-doped InSe FETs using 2-terminal configuration under 532 nm and 785 nm excitation. Low temperature measurements were also studied ranging from 295 K to $\sim$13 K in a cryostat. Transport measurements showed little to no current when drain-source and back-gate voltages were applied and under low temperature. Low temperature PL showed blue-shifted peaks at T $>$ 50 K and red-shifted peaks at T $

Download or read book Electronic Properties of Multilayers and Low Dimensional Semiconductor Structures written by J.M. Chamberlain and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 477 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Advanced Study Institute on the Electronic Properties of Multilayers and Low Dimensional Semiconductor Structures focussed on several of the most active areas in modern semiconductor physics. These included resonant tunnelling and superlattice phenomena and the topics of ballistic transport, quantised conductance and anomalous magnetoresistance effects in laterally gated two-dimensional electron systems. Although the main emphasis was on fundamental physics, a series of supporting lectures described the underlying technology (Molecular Beam Epitaxy, Metallo-Organic Chemical Vapour Deposition, Electron Beam Lithography and other advanced processing technologies). Actual and potential applications of low dimensional structures in optoelectronic and high frequency devices were also discussed. The ASI took the form of a series of lectures of about fifty minutes' duration which were given by senior researchers from a wide range of countries. Most of the lectures are recorded in these Proceedings. The younger members of the Institute made the predominant contribution to the discussion sessions following each lecture and, in addition, provided most of the fifty-five papers that were presented in two lively poster sessions. The ASl emphasised the impressive way in which this research field has developed through the fruitful interaction of theory, experiment and semiconductor device technology. Many of the talks demonstrated both the effectiveness and limitations of semiclassical concepts in describing the quantum phenomena exhibited by electrons in low dimensional structures.

Download or read book Optical Spectroscopy of Low Dimensional Semiconductors written by G. Abstreiter and published by Springer. This book was released on 1997-09-30 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of a September 1996 meeting, in sections on quantum films and superlattices, quantum wires, and quantum dots. Coverage includes basic physics aspects, novel technology and material fabrication tools, characterization methods, and new devices, with special attention to quantum wire and quantum dot lasers. Specific topics include inelastic light scattering by electrons in low-dimensional semiconductors, band-gap renormalization in quasi-one-dimensional systems, conductance in nanowires, and fabrication of quantum dots for semiconductor lasers with confined electrons and photons. Annotation copyrighted by Book News, Inc., Portland, OR

Download or read book Fundamentals of Low Dimensional Magnets written by Ram K. Gupta and published by CRC Press. This book was released on 2022-08-29 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: A low-dimensional magnet is a key to the next generation of electronic devices. In some respects, low-dimensional magnets refer to nanomagnets (nanostructured magnets) or single-molecule magnets (molecular nanomagnets). They also include the group of magnetic nanoparticles, which have been widely used in biomedicine, technology, industries, and environmental remediation. Low-dimensional magnetic materials can be used effectively in the future in powerful computers (hard drives, magnetic random-access memory, ultra-low power consumption switches, etc.). The properties of these materials largely depend on the doping level, phase, defects, and morphology. This book covers various nanomagnets and magnetic materials. The basic concepts, various synthetic approaches, characterizations, and mathematical understanding of nanomaterials are provided. Some fundamental applications of 1D, 2D, and 3D materials are covered. This book provides the fundamentals of low-dimensional magnets along with synthesis, theories, structure-property relations, and applications of ferromagnetic nanomaterials. This book broadens our fundamental understanding of ferromagnetism and mechanisms for realization and advancement in devices with improved energy efficiency and high storage capacity.