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Electronic And Spintronic Transport In Germanium Nanostructures
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Book Synopsis Electronic and Spintronic Transport in Germanium Nanostructures by : En-Shao Liu
Download or read book Electronic and Spintronic Transport in Germanium Nanostructures written by En-Shao Liu and published by . This book was released on 2014 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: The digital information processing system has benefited tremendously from the invention and development of complementary metal-oxide-semiconductor (CMOS) integrated circuits. The relentless scaling of the physical dimensions of transistors has been consistently delivering improved overall circuit density and performance every technology generation. However, the continuation of this trend is in question for silicon-based transistors when quantum mechanical tunneling becomes more relevant; further scaling in feature sizes can lead to increased leakage current and power dissipation. Numerous research efforts have been implemented to address these scaling challenges, either by aiming to increase the performance at the transistor level or to introduce new functionalities at the circuit level. In the first approach, novel materials and device structures are explored to improve the performance of CMOS transistors, including the use of high-mobility materials (e.g. III-V compounds and germanium) as the channel, and multi-gate structures. On the other hand, the overall circuit capability could be increased if other state variables are exploited in the electronic devices, such as the electron spin degree of freedom (e.g. spintronics). Here we explore the potential of germanium nanowires in both CMOS and beyond-CMOS applications, studying the electronic and spintronic transport in this material system. Germanium is an attractive replacement to silicon as the channel material in CMOS technology, thanks to its lighter effective electron and hole mass. The nanowire structures, directly synthesized using chemical vapor deposition, provide a natural platform for multi-gate structures in which the electrostatic control of the gate is enhanced. We present the realization and scaling properties of germanium-silicon-germanium core-shell nanowire n-type, [omega]-gate field-effect transistors (FETs). By studying the channel length dependence of NW FET characteristics, we conclude that the intrinsic channel resistance is the main limiting factor of the drive current of Ge NW n-FETs. Utilizing the electron spins in semiconductor devices can in principle enhance overall circuit performance and functionalities. Electrical injection of spin-polarized electrons into a semiconductor, large spin diffusion length, and an integration friendly platform are desirable ingredients for spin based-devices. Here we demonstrate lateral spin injection and detection in Ge NWs, by using ferromagnetic metal contacts and tunnel barriers for contact resistance engineering. We map out the contact resistance window for which spin transport is observed, manifestly showing the conductivity matching required for spin injection.
Book Synopsis Semiconductor Spintronics and Quantum Computation by : D.D. Awschalom
Download or read book Semiconductor Spintronics and Quantum Computation written by D.D. Awschalom and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: The past few decades of research and development in solid-state semicon ductor physics and electronics have witnessed a rapid growth in the drive to exploit quantum mechanics in the design and function of semiconductor devices. This has been fueled for instance by the remarkable advances in our ability to fabricate nanostructures such as quantum wells, quantum wires and quantum dots. Despite this contemporary focus on semiconductor "quantum devices," a principal quantum mechanical aspect of the electron - its spin has it accounts for an added quan largely been ignored (except in as much as tum mechanical degeneracy). In recent years, however, a new paradigm of electronics based on the spin degree of freedom of the electron has begun to emerge. This field of semiconductor "spintronics" (spin transport electron ics or spin-based electronics) places electron spin rather than charge at the very center of interest. The underlying basis for this new electronics is the intimate connection between the charge and spin degrees of freedom of the electron via the Pauli principle. A crucial implication of this relationship is that spin effects can often be accessed through the orbital properties of the electron in the solid state. Examples for this are optical measurements of the spin state based on the Faraday effect and spin-dependent transport measure ments such as giant magneto-resistance (GMR). In this manner, information can be encoded in not only the electron's charge but also in its spin state, i. e.
Book Synopsis Electrical Spin Injection and Detection in Ge Nanowires and Toplogical Insulators by : Jianshi Tang
Download or read book Electrical Spin Injection and Detection in Ge Nanowires and Toplogical Insulators written by Jianshi Tang and published by . This book was released on 2014 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: The continuous scaling of Si transistor feature size has driven the advancement of semiconductor technology in the past decades; however, such aggressive scaling is approaching the ultimate physical limit soon. Novel materials and devices are in urgent need to resolve a number of critical challenges. In particular, spintronic devices have been proposed and extensively studied by using the spin of electrons as another degree of freedom in devices for information processing, which enables advanced electronic devices that could potentially outperform Si devices with lower power dissipation and faster switching. In this work, the carrier and spin transport in Ge nanowires will be presented. Atomic-scale thermal annealing was established as a convenient approach to make high-quality nanoscale source/drain contacts in high-performance Ge nanowire transistors. Electrical spin injection and detection in both p- and n-type Ge nanowires were demonstrated using ferromagnetic Mn5Ge3 Schottky contacts and Fe/MgO tunnel junctions, respectively. The measured spin lifetime and spin diffusion length in Ge nanowires were much larger than those reported for bulk Ge, suggesting that the spin relaxation was significantly suppressed in nanowires. Furthermore, we studied the spin transport in topological insulators, in which the spin-momentum locking of helical surface states was preserved by the strong spin-orbit interaction and time-reversal symmetry. We demonstrated the electrical detection of the spin-polarized surface states conduction in topological insulator (Bi0.53Sb0.47)2Te3 using a Co/Al2O3 ferromagnetic tunnel contact. Voltage (resistance) hysteresis was observed when sweeping the magnetic field, and the two resistance states were reversible by changing the electric current direction. Our results showed a direct evidence of the charge current-induced spin polarization in the topological surface states. With the understanding of spin injection and detection, it might open up great opportunities to explore novel spintronic devices based on topological insulators and Ge nanowires.
Book Synopsis Silicon-Germanium (SiGe) Nanostructures by : Y. Shiraki
Download or read book Silicon-Germanium (SiGe) Nanostructures written by Y. Shiraki and published by Elsevier. This book was released on 2011-02-26 with total page 649 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured silicon-germanium (SiGe) opens up the prospects of novel and enhanced electronic device performance, especially for semiconductor devices. Silicon-germanium (SiGe) nanostructures reviews the materials science of nanostructures and their properties and applications in different electronic devices. The introductory part one covers the structural properties of SiGe nanostructures, with a further chapter discussing electronic band structures of SiGe alloys. Part two concentrates on the formation of SiGe nanostructures, with chapters on different methods of crystal growth such as molecular beam epitaxy and chemical vapour deposition. This part also includes chapters covering strain engineering and modelling. Part three covers the material properties of SiGe nanostructures, including chapters on such topics as strain-induced defects, transport properties and microcavities and quantum cascade laser structures. In Part four, devices utilising SiGe alloys are discussed. Chapters cover ultra large scale integrated applications, MOSFETs and the use of SiGe in different types of transistors and optical devices. With its distinguished editors and team of international contributors, Silicon-germanium (SiGe) nanostructures is a standard reference for researchers focusing on semiconductor devices and materials in industry and academia, particularly those interested in nanostructures. Reviews the materials science of nanostructures and their properties and applications in different electronic devices Assesses the structural properties of SiGe nanostructures, discussing electronic band structures of SiGe alloys Explores the formation of SiGe nanostructuresfeaturing different methods of crystal growth such as molecular beam epitaxy and chemical vapour deposition
Book Synopsis Mesoscopic Electronics in Solid State Nanostructures by : Thomas Heinzel
Download or read book Mesoscopic Electronics in Solid State Nanostructures written by Thomas Heinzel and published by John Wiley & Sons. This book was released on 2008-07-11 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text treats electronic transport in the regime where conventional textbook models are no longer applicable, including the effect of electronic phase coherence, energy quantization and single-electron charging. This second edition is completely updated and expanded, and now comprises new chapters on spin electronics and quantum information processing, transport in inhomogeneous magnetic fields, organic/molecular electronics, and applications of field effect transistors. The book also provides an overview of semiconductor processing technologies and experimental techniques. With a number of examples and problems with solutions, this is an ideal introduction for students and beginning researchers in the field. "This book is a useful tool, too, for the experienced researcher to get a summary of recent developments in solid state nanostructures. I applaud the author for a marvellous contribution to the scientific community of mesoscopic electronics." Prof. K. Ensslin, Solid State Physics Laboratory, ETH Zurich
Book Synopsis Spin-polarized Transport and Spin Filtering in Organic Nanostructures by : Kazi Monirul Alam Alam
Download or read book Spin-polarized Transport and Spin Filtering in Organic Nanostructures written by Kazi Monirul Alam Alam and published by . This book was released on 2014 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrons, the fundamental charge carriers in solid-state devices, possess three intrinsic properties: mass, charge and spin. Spin is a quantum mechanical property, but can be loosely visualized as a tiny "intrinsic" magnetic dipole moment attached to an electron. In conventional electron devices, spin magnetic moments point along random directions in space and play no significant role in device operation. In the emerging field of "spintronics" the central theme is to harness the spin degree of freedom of charge carriers to realize novel data storage and information processing technologies. Spintronic devices are already ubiquitous in state-of-the-art hard disks with large storage densities. A concerted global effort is underway to explore various spin-based information processing concepts, which can potentially be more energy-efficient than traditional charge-based electronics. In recent years, substantial research has been devoted to understanding carrier spin dynamics in metallic multilayers, tunnel junctions and inorganic semiconductors such as silicon, germanium and various III-V compounds. On the other hand, p-conjugated organic semiconductors that play a crucial role in organic electronics and displays are relatively new materials in the area of spintronics. Organic semiconductors offer several advantages (such as mechanical flexibility, chemical tunability of physical properties, low-cost and low-temperature processing) compared to their inorganic counterparts. The ability to control carrier spin dynamics in organic materials will open up possibility of new devices such as flexible non-volatile memories, spin-based organic light emitting diodes and spin filters. iii In this work, we have explored two key spin related phenomena in organic semiconductor nanostructures: (a) spin-polarized transport and (b) spin filtering. In the first sub-project, we explore spin transport in "nanowire" geometry instead of commonly studied thin film devices. Such experiments shed light on the spin relaxation mechanisms in organics and indicate ways to minimize such effects. Fabrication of organic nanowires with well-controlled geometry in the sub-100 nm range is a non-trivial task, and in this subproject we have developed a novel technique for this purpose. Spin transport in rubrene nanowires has been studied, which indicates significant suppression of spin relaxation in nanowire geometry compared to rubrene thin films. Our experimental data indicates that spin-orbit coupling is the dominant spin relaxation mechanism in rubrene nanowires. In the second sub-project, we explore spin filtering (transmission of one particular type of spin) through an organic nanostructure in which single wall carbon nanotubes (SWCNT) are wrapped with single stranded DNA (ssDNA) molecules. Efficient spin filtering has been observed in this system, which may enable magnetless spintronic devices in the future.
Book Synopsis Electronic Quantum Transport in Mesoscopic Semiconductor Structures by : Thomas Ihn
Download or read book Electronic Quantum Transport in Mesoscopic Semiconductor Structures written by Thomas Ihn and published by Springer Science & Business Media. This book was released on 2004-01-08 with total page 267 pages. Available in PDF, EPUB and Kindle. Book excerpt: Opening with a brief historical account of electron transport from Ohm's law through transport in semiconductor nanostructures, this book discusses topics related to electronic quantum transport. The book is written for graduate students and researchers in the field of mesoscopic semiconductors or in semiconductor nanostructures. Highlights include review of the cryogenic scanning probe techniques applied to semiconductor nanostructures.
Book Synopsis Spintronics Handbook, Second Edition: Spin Transport and Magnetism by : Evgeny Y. Tsymbal
Download or read book Spintronics Handbook, Second Edition: Spin Transport and Magnetism written by Evgeny Y. Tsymbal and published by CRC Press. This book was released on 2019-05-20 with total page 619 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition offers an update on the single most comprehensive survey of the two intertwined fields of spintronics and magnetism, covering the diverse array of materials and structures, including silicon, organic semiconductors, carbon nanotubes, graphene, and engineered nanostructures. It focuses on seminal pioneering work, together with the latest in cutting-edge advances, notably extended discussion of two-dimensional materials beyond graphene, topological insulators, skyrmions, and molecular spintronics. The main sections cover physical phenomena, spin-dependent tunneling, control of spin and magnetism in semiconductors, and spin-based applications.
Book Synopsis Charge and Spin Transport in Disordered Graphene-Based Materials by : Dinh Van Tuan
Download or read book Charge and Spin Transport in Disordered Graphene-Based Materials written by Dinh Van Tuan and published by Springer. This book was released on 2015-10-22 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an in-depth theoretical analysis of charge and spin transport properties in complex forms of disordered graphene. It relies on innovative real space computational methods of the time-dependent spreading of electronic wave packets. First a universal scaling law of the elastic mean free path versus the average grain size is predicted for polycrystalline morphologies, and charge mobilities of up to 300.000 cm2/V.s are determined for 1 micron grain size, while amorphous graphene membranes are shown to behave as Anderson insulators. An unprecedented spin relaxation mechanism, unique to graphene and driven by spin/pseudospin entanglement is then reported in the presence of weak spin-orbit interaction (gold ad-atom impurities) together with the prediction of a crossover from a quantum spin Hall Effect to spin Hall effect (for thallium ad-atoms), depending on the degree of surface ad-atom segregation and the resulting island diameter.
Download or read book Spin Current written by Sadamichi Maekawa and published by Oxford University Press. This book was released on 2017 with total page 541 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a new branch of physics and technology, called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called "spin current", are manipulated and controlled together. This book is intended to provide an introduction and guide to the new physics and applications of spin current.
Book Synopsis Review by : Oak Ridge National Laboratory
Download or read book Review written by Oak Ridge National Laboratory and published by . This book was released on 2002 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Spin Coherence in Semiconductor Nanostructures by :
Download or read book Spin Coherence in Semiconductor Nanostructures written by and published by . This book was released on 2006 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report progress in calculations of spin coherence and spin transport properties in nanoscale geometries, including calculations of g-factors in quantum dots, exchange interactions in Si/Ge quantum dots, tuning of spin coherence times for electron spin, tuning of dipolar magnetic fields for nuclear spin, spontaneous spin polarization generation and new designs for spin-based teleportation and spin transistors. Our new proposal for electron-spin based teleportation is mediated by single photons and does not require correlated photon detection (Bell detection). We find that electric transport in nonmagnetic semiconductors is unstable to the formation of spin polarized packets at room temperature. We also predict that orbital angular momentum quenching in quantum dots will drive g factors closer to 2 than previously expected. These calculations may be of use in semiconductor spintronic devices or quantum computation.
Book Synopsis Spin-dependent Transport in Graphene Nanostructures by : Jan Bundesmann
Download or read book Spin-dependent Transport in Graphene Nanostructures written by Jan Bundesmann and published by Universitatsverlag Regensburg. This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Graphene, a two-dimensional material consisting of carbon atoms arranged in a honeycomb lattice, has become famous for the evidence that its electronic structure approximately corresponds to the one of massless Dirac fermions. However, in order to correctly describe graphene , the spin, which plays an essential role in the physics of Dirac fermions, has to be replaced by the so-called pseudospin, an intrinsic property of the honeycomb lattice which is not related to the electrons' real spin. If, now, the real spin is considered, too, the effective Hamiltonian has to be extended by terms which have no equivalents in the original Dirac Hamiltonian. While charge transport properties can be predicted from Dirac physics very realiably, the extended Hamiltonian leads to new phenomena in the context of spin transport. In this thesis two distinct topics are investigated theoretically. The presented results are mainly based on numerical simulations using a recursive Green's function algorithm. The first part of this thesis covers spin relaxation in graphene. Different sources of spin relaxation are investigated with a particular focus on the role of locally varying spin-orbit coupling and adatoms. The second part covers edge magnetism in graphene zigzag nanoribbons. It is shown how magnetic clusters form even in the presence of a potential which is not homogeneous in space. Different signatures of zigzag edge magnetization on charge and spin transport are presented.
Book Synopsis Handbook of Spin Transport and Magnetism by : Evgeny Y. Tsymbal
Download or read book Handbook of Spin Transport and Magnetism written by Evgeny Y. Tsymbal and published by CRC Press. This book was released on 2016-04-19 with total page 797 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past several decades, the research on spin transport and magnetism has led to remarkable scientific and technological breakthroughs, including Albert Fert and Peter Grunberg's Nobel Prize-winning discovery of giant magnetoresistance (GMR) in magnetic metallic multilayers. Handbook of Spin Transport and Magnetism provides a comprehensive, bal
Book Synopsis Ge/Si Nanostructures for Electronic and Optoelectronic Devices by : Atanu Bag
Download or read book Ge/Si Nanostructures for Electronic and Optoelectronic Devices written by Atanu Bag and published by LAP Lambert Academic Publishing. This book was released on 2012-06 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growth of semiconductor nanostructures and the study of their properties have been very active areas of research nano-device application. These novel nanostructures offer interesting prospects for the development of new electronic and photonic devices. Silicon micro photonics, a technology that merges photonics and silicon microelectronic components, is rapidly evolving. The main challenge is to develop efficient light sources out of silicon or silicon based materials. This allows one to combine the information-processing and information transport capabilities of electrons and photons on a Si-chip. The extension of research interests to germanium based nanostructures is rather straightforward, due to its higher carrier mobilities, higher excitonic Bohr radius and capability in forming group-IV heterostructures on Si substrates. During the course of this book, we have undertaken a systematic study on the synthesis and characteristics of Si/Ge based nanostructures for optical and electronic device applications.
Book Synopsis Electronic, Spintronic and Transport Properties Og Carbon Based Nanowires by : Ozan Arı
Download or read book Electronic, Spintronic and Transport Properties Og Carbon Based Nanowires written by Ozan Arı and published by . This book was released on 2011 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, properties of carbon based nanowires are studied by ab-initio calculations. The aim is to gain a thorough understanding of the electronic, spintronic, transport properties in nanowires and how they are affected by different geometric formations, defects and adatom adsorptions. To this end the non-equilibrium Green's function formalism with first principles pseudopotential density functional theory calculations have been used to describe spin-polarized systems. Firstly, different geometric formations of Cobalt-Benzene nanowires are investigated. Systems with ferromagnetic ordering are calculated as half-metallic while systems with antiferromagnetic ordering behave as metallic. Also the results of the spin polarized current calculations indicate that one of the spin components of current is dominant for the antiferromagnetic systems while both spin components of current are dominant in different bias windows of a specific total applied bias. As second case, alkali atom termination of the zigzag graphene nanoribbons (ZGNR) are studied. In particular, using sodium atoms for the saturation of ZGNR edges at half the concentration of edge-carbon atoms make it a one dimensional, perfect semimetal, where the valance and conduction bands meet at only a single, Dirac-like point. Unlike pristine graphene, the Dirac-"cones" of Na-ZGNR is not symmetric with respect to wave vector, but rather it is tilted. Finally, adsorption up to the graphenic sheets with periodic 5-8 defects is studied. Especially, electronic structure of the V adsorption into 5-8 defects induced graphenic sheets are calculated as half-metallic while formation of linear bands crossing at the Fermi level which form a tilted Dirac cone.
Book Synopsis Handbook of Spintronics by : Yongbing Xu
Download or read book Handbook of Spintronics written by Yongbing Xu and published by Springer. This book was released on 2015-10-14 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over two volumes and 1500 pages, the Handbook of Spintronics will cover all aspects of spintronics science and technology, including fundamental physics, materials properties and processing, established and emerging device technology and applications. Comprising 60 chapters from a large international team of leading researchers across academia and industry, the Handbook provides readers with an up-to-date and comprehensive review of this dynamic field of research. The opening chapters focus on the fundamental physical principles of spintronics in metals and semiconductors, including an introduction to spin quantum computing. Materials systems are then considered, with sections on metallic thin films and multilayers, magnetic tunnelling structures, hybrids, magnetic semiconductors and molecular spintronic materials. A separate section reviews the various characterisation methods appropriate to spintronics materials, including STM, spin-polarised photoemission, x-ray diffraction techniques and spin-polarised SEM. The third part of the Handbook contains chapters on the state of the art in device technology and applications, including spin valves, GMR and MTJ devices, MRAM technology, spin transistors and spin logic devices, spin torque devices, spin pumping and spin dynamics and other topics such as spin caloritronics. Each chapter considers the challenges faced by researchers in that area and contains some indications of the direction that future work in the field is likely to take. This reference work will be an essential and long-standing resource for the spintronics community.
