Download or read book Simulation of Thermal Transport in Semiconductor Nanostructures written by Song Mei and published by . This book was released on 2017 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the advancement of nanofabrication techniques, the sizes of semiconductor electronic and optoelectronic devices keep decreasing while the operating speeds keep increasing. High-speed operation leads to more heat generation and puts more thermal stress on the devices. Since the heat conduction in semiconductors is dominated by the lattice (i.e., phonons), understanding phonon transport in nanostructures is essential to addressing and alleviating the thermal-stress problem in these modern devices. In addition to the increased thermal stress, the advanced techniques that have allowed for the shrinking of the devices routinely rely on heterostructuring, doping, alloying, and the growth of intentionally strained layers to achieve the desired electronic and optical properties. These introduce impediments to phonon transport such as boundaries, interfaces, point defects (alloy atoms or dopants), and strain. Phonon transport is strongly affected by this nanoscale disorder. This dissertation examines how different types of disorder interact with phonons and degrade phonon transport. First, we study thermal transport in graphene nanoribbons (GNRs). GNRs are quasi-one-dimensional (quasi-1D) systems where the edges (boundaries) play an important role in reducing thermal conductivity. Additionally, the thermal transport in GNRs is anisotropic and depend on the GNR's chirality (GNR orientation and edge termination). We use phonon Monte Carlo (PMC) with full phonon dispersions to describe two highly-symmetric types of GNRs: the armchair GNR (AGNR) and the zigzag GNR (ZGNR). PMC tracks phonon in real space and we can explicitly include non-trivial edge structures. Moreover, the relatively low computational burden of PMC allows us to simulate samples up to 100 $\mu$m in length and predict an upper limit for thermal conductivity in graphene. We then investigate the thermal conductivity in III-V superlattices (SLs). SLs consist of alternating thin layers of different materials and III-V SLs are widely used in nanoscale thermoelectric and optoelectronic devices. The key feature in SLs is that it contains many interfaces, which dictates thermal transport. As III-V SLs are often fabricated using well-controlled techniques and have high-quality interfaces, we develop a model with only one free parameter---the effective rms roughness of the interfaces---to describe its twofold influence: reducing the in-plane layer thermal conductivity and introducing thermal boundary resistance (TBR) in the cross-plane direction. Both the calculated in-plane and cross-plane thermal conductivity of SLs agree with a number of different experiments. Finally, we study thermal conductivity of ternary III-V alloys. In modern optoelectronic devices, ternary III-V alloys are used more often than binary compounds because one can use composition engineering to achieve different effective masses, electron/hole barrier heights, and strain levels. Ternary alloys are usually treated under the virtual crystal approximation (VCA) where cation atoms are assumed to be randomly distributed and possess an averaged mass. This assumption is challenged by a discrepancy between different experiments, as well as the discrepancy between experiments and calculations. We use molecular dynamics (MD) to study the ternary alloy system as both atom masses and atom locations are explicitly tracked in MD. We discover that the thermal conductivity is determined by a competition between mass-difference scattering and the short-range ordering of the cations.
Download or read book Nanophononics written by Zlatan Aksamija and published by CRC Press. This book was released on 2017-11-22 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat in most semiconductor materials, including the traditional group IV elements (Si, Ge, diamond), III–V compounds (GaAs, wide-bandgap GaN), and carbon allotropes (graphene, CNTs), as well as emerging new materials like transition metal dichalcogenides (TMDCs), is stored and transported by lattice vibrations (phonons). Phonon generation through interactions with electrons (in nanoelectronics, power, and nonequilibrium devices) and light (optoelectronics) is the central mechanism of heat dissipation in nanoelectronics. This book focuses on the area of thermal effects in nanostructures, including the generation, transport, and conversion of heat at the nanoscale level. Phonon transport, including thermal conductivity in nanostructured materials, as well as numerical simulation methods, such as phonon Monte Carlo, Green’s functions, and first principles methods, feature prominently in the book, which comprises four main themes: (i) phonon generation/heat dissipation, (i) nanoscale phonon transport, (iii) applications/devices (including thermoelectrics), and (iv) emerging materials (graphene/2D). The book also covers recent advances in nanophononics—the study of phonons at the nanoscale. Applications of nanophononics focus on thermoelectric (TE) and tandem TE/photovoltaic energy conversion. The applications are augmented by a chapter on heat dissipation and self-heating in nanoelectronic devices. The book concludes with a chapter on thermal transport in nanoscale graphene ribbons, covering recent advances in phonon transport in 2D materials. The book will be an excellent reference for researchers and graduate students of nanoelectronics, device engineering, nanoscale heat transfer, and thermoelectric energy conversion. The book could also be a basis for a graduate special topics course in the field of nanoscale heat and energy.
Download or read book Phonon Thermal Transport in Silicon Based Nanomaterials written by Hai-Peng Li and published by Springer. This book was released on 2018-09-08 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this Brief, authors introduce the advance in theoretical and experimental techniques for determining the thermal conductivity in nanomaterials, and focus on review of their recent theoretical studies on the thermal properties of silicon–based nanomaterials, such as zero–dimensional silicon nanoclusters, one–dimensional silicon nanowires, and graphenelike two–dimensional silicene. The specific subject matters covered include: size effect of thermal stability and phonon thermal transport in spherical silicon nanoclusters, surface effects of phonon thermal transport in silicon nanowires, and defects effects of phonon thermal transport in silicene. The results obtained are supplemented by numerical calculations, presented as tables and figures. The potential applications of these findings in nanoelectrics and thermoelectric energy conversion are also discussed. In this regard, this Brief represents an authoritative, systematic, and detailed description of the current status of phonon thermal transport in silicon–based nanomaterials. This Brief should be a highly valuable reference for young scientists and postgraduate students active in the fields of nanoscale thermal transport and silicon-based nanomaterials.
Download or read book Predicting Phonon Transport in Semiconductor Nanostructures Using Atomistic Calculations and the Boltzmann Transport Equation written by Daniel P. Sellan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nano scale Heat Transfer in Nanostructures written by Jihong Al-Ghalith and published by Springer. This book was released on 2018-03-06 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book introduces modern atomistic techniques for predicting heat transfer in nanostructures, and discusses the applications of these techniques on three modern topics. The study of heat transport in screw-dislocated nanowires with low thermal conductivity in their bulk form represents the knowledge base needed for engineering thermal transport in advanced thermoelectric and electronic materials, and suggests a new route to lower thermal conductivity that could promote thermoelectricity. The study of high-temperature coating composite materials facilitates the understanding of the role played by composition and structural characterization, which is difficult to approach via experiments. And the understanding of the impact of deformations, such as bending and collapsing on thermal transport along carbon nanotubes, is important as carbon nanotubes, due to their exceptional thermal and mechanical properties, are excellent material candidates in a variety of applications, including thermal interface materials, thermal switches and composite materials.
Download or read book Nanostructured Semiconductors written by Konstantinos Termentzidis and published by CRC Press. This book was released on 2017-09-01 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book is devoted to nanostructures and nanostructured materials containing both amorphous and crystalline phases with a particular focus on their thermal properties. It is the first time that theoreticians and experimentalists from different domains gathered to treat this subject. It contains two distinct parts; the first combines theory and simulations methods with specific examples, while the second part discusses methods to fabricate nanomaterials with crystalline and amorphous phases and experimental techniques to measure the thermal conductivity of such materials. Physical insights are given in the first part of the book, related with the existing theoretical models and the state of art simulations methods (molecular dynamics, ab-initio simulations, kinetic theory of gases). In the second part, engineering advances in the nanofabrication of crystalline/amorphous heterostructures (heavy ion irradiation, electrochemical etching, aging/recrystallization, ball milling, PVD, laser crystallization and magnetron sputtering) and adequate experimental measurement methods are analyzed (Scanning Thermal Microscopy, Raman, thermal wave methods and x-rays neutrons spectroscopy).
Download or read book Thermal Transport for Applications in Micro Nanomachining written by Basil T. Wong and published by Springer Science & Business Media. This book was released on 2008-07-19 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Beginning with an overview of nanomachining, this monograph introduces the relevant concepts from solid-state physics, thermodynamics, and lattice structures. It then covers modeling of thermal transport at the nanoscale and details simulations of different processes relevant to nanomachining. The final chapter summarizes the important points and discusses directions for future work to improve the modeling of nanomachining.
Download or read book Thermal Transport in Semiconductors written by Pol Torres Alvarez and published by Springer. This book was released on 2018-06-28 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting from a broad overview of heat transport based on the Boltzmann Transport Equation, this book presents a comprehensive analysis of heat transport in bulk and nanomaterials based on a kinetic-collective model (KCM). This has become key to understanding the field of thermal transport in semiconductors, and represents an important stride. The book describes how heat transport becomes hydrodynamic at the nanoscale, propagating very much like a viscous fluid and manifesting vorticity and friction-like behavior. It introduces a generalization of Fourier’s law including a hydrodynamic term based on collective behavior in the phonon ensemble. This approach makes it possible to describe in a unifying way recent experiments that had to resort to unphysical assumptions in order to uphold the validity of Fourier’s law, demonstrating that hydrodynamic heat transport is a pervasive type of behavior in semiconductors at reduced scales.
Download or read book Molecular Dynamics Simulations of Thermal Transport in Silicon based Nanostructures written by Rafael Frieling and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theory of Transport Properties of Semiconductor Nanostructures written by Eckehard Schöll and published by Springer. This book was released on 2014-03-14 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in the fabrication of semiconductors have created almost un limited possibilities to design structures on a nanometre scale with extraordinary electronic and optoelectronic properties. The theoretical understanding of elec trical transport in such nanostructures is of utmost importance for future device applications. This represents a challenging issue of today's basic research since it requires advanced theoretical techniques to cope with the quantum limit of charge transport, ultrafast carrier dynamics and strongly nonlinear high-field ef fects. This book, which appears in the electronic materials series, presents an over view of the theoretical background and recent developments in the theory of electrical transport in semiconductor nanostructures. It contains 11 chapters which are written by experts in their fields. Starting with a tutorial introduction to the subject in Chapter 1, it proceeds to present different approaches to transport theory. The semiclassical Boltzmann transport equation is in the centre of the next three chapters. Hydrodynamic moment equations (Chapter 2), Monte Carlo techniques (Chapter 3) and the cellular au tomaton approach (Chapter 4) are introduced and illustrated with applications to nanometre structures and device simulation. A full quantum-transport theory covering the Kubo formalism and nonequilibrium Green's functions (Chapter 5) as well as the density matrix theory (Chapter 6) is then presented.
Download or read book First Principles based Molecular Modeling of Thermal Transport in Silicon based Nanomaterials written by Yongjin Lee and published by . This book was released on 2014 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: In today's nanotechnology, a critical issue is to gain the ability to control the structure and function of matter with a deeper understanding of the quantitative and qualitative relationship among their synthesis conditions, structures, and properties. Experiments may provide information regarding the behavior of nanomaterials, but their interpretations are often controversial due largely to the difficulty of direct measurement. Hereupon, with the amazing advance in computer technology since the late 20th century, computational modeling in science and engineering is increasingly important particularly in the fields of nanoscience and nanotechnology while it can provide researchers with significant insights into atomic-level interactions in various materials systems and underlying fundamental theories. The ability of engineering thermal conductivity of materials on the nanoscale has become extremely important in various applications including electronics and energy storage/conversion technologies. Due to technical difficulties in experimentally measuring the thermal conductivity of disordered and complex nanostructures, there has been much interest in use of theoretical and computational methods to investigate thermal transport properties nanostructured materials. One computational method that can perform an accurate analysis for the thermal conductivity of new or complex systems is molecular dynamics (MD), due to its capability of predicting the behaviors of atoms in large systems. In this work, we have developed a comprehensive MD-based computational platform capable of predicting and explaining thermal transport in disordered and complex nanostructured materials. The unique features include construction of realistic nanostructures, determination of reliable force fields, and direct simulation of large systems, which are allowed by coupling various state-of-the-art computational methods including quantum mechanics, molecular mechanics, statistical theories, and massively parallel computing. The computational scheme was applied to describe thermal transport in various silicon and carbon-based disordered and nanostructures. First, the effects of defects including vacancy clusters, substitutional dopants, and dopant-defect complexes on the thermal conductivity of bulk crystalline silicon were investigated. Next, we analyzed the factors affecting heat transport in silicon-germanium and ternary silicon-germanium-tin alloys. Lastly, we performed the analysis of heat transport in silicon-based nanostructures such as nanowires and polycrystalline structures.
Download or read book The Physics of Phonons written by Gyaneshwar P. Srivastava and published by Routledge. This book was released on 2019-07-16 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: There have been few books devoted to the study of phonons, a major area of condensed matter physics. The Physics of Phonons is a comprehensive theoretical discussion of the most important topics, including some topics not previously presented in book form. Although primarily theoretical in approach, the author refers to experimental results wherever possible, ensuring an ideal book for both experimental and theoretical researchers. The author begins with an introduction to crystal symmetry and continues with a discussion of lattice dynamics in the harmonic approximation, including the traditional phenomenological approach and the more recent ab initio approach, detailed for the first time in this book. A discussion of anharmonicity is followed by the theory of lattice thermal conductivity, presented at a level far beyond that available in any other book. The chapter on phonon interactions is likewise more comprehensive than any similar discussion elsewhere. The sections on phonons in superlattices, impure and mixed crystals, quasicrystals, phonon spectroscopy, Kapitza resistance, and quantum evaporation also contain material appearing in book form for the first time. The book is complemented by numerous diagrams that aid understanding and is comprehensively referenced for further study. With its unprecedented wide coverage of the field, The Physics of Phonons will be indispensable to all postgraduates, advanced undergraduates, and researchers working on condensed matter physics.
Download or read book Theory of Transport Properties of Semiconductor Nanostructures written by Eckehard Schöll and published by Springer Science & Business Media. This book was released on 1997-12-31 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in the fabrication of semiconductors have created almost un limited possibilities to design structures on a nanometre scale with extraordinary electronic and optoelectronic properties. The theoretical understanding of elec trical transport in such nanostructures is of utmost importance for future device applications. This represents a challenging issue of today's basic research since it requires advanced theoretical techniques to cope with the quantum limit of charge transport, ultrafast carrier dynamics and strongly nonlinear high-field ef fects. This book, which appears in the electronic materials series, presents an over view of the theoretical background and recent developments in the theory of electrical transport in semiconductor nanostructures. It contains 11 chapters which are written by experts in their fields. Starting with a tutorial introduction to the subject in Chapter 1, it proceeds to present different approaches to transport theory. The semiclassical Boltzmann transport equation is in the centre of the next three chapters. Hydrodynamic moment equations (Chapter 2), Monte Carlo techniques (Chapter 3) and the cellular au tomaton approach (Chapter 4) are introduced and illustrated with applications to nanometre structures and device simulation. A full quantum-transport theory covering the Kubo formalism and nonequilibrium Green's functions (Chapter 5) as well as the density matrix theory (Chapter 6) is then presented.
Download or read book Simulation of Thermal Effects in Semiconductor Materials and Devices written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermal Transport in Low Dimensional Semiconductor Nanostructures written by Jaime Bohórquez-Ballén and published by . This book was released on 2014 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have performed a first principles density functional theory (DFT) calculations to study the thermal conductivity in ZnO nanotubes, ZnO nanowires, and Si/Ge shell-core nanowires. We found the equilibrium configuration and the electric band structure of each nanostructure using DFT, the interatomic force constants and the phonon dispersion relations were calculated using DFPT as implemented in Quantum Espresso. In order to fundamentally understand the effect of atomic arrangements, we calculated the phonon conductance in a ballistic approach using a Green's function method. All ZnO nanostructures studied exhibit semiconducting behavior, with direct bandgap at the Gamma point. The calculated values for the bandgaps were larger than the value of the bandgap of the bulk ZnO. We were able to identify phonon modes in which the motion of Zn atoms is significant when it is compared with the motion of oxygen atoms. The thermal conductivity depends on the diameter of the nanowires and nanotubes and it is dramatically affected when the nanowire or nanotube is doped with Ga. For Si/Ge nanowires, the slope and the curvature of acoustic modes in the phonon dispersion relation increases when the diameter increases. For nanowires with the same number of atoms, the slope and curvature of acoustic modes depends on the concentration of Si atoms. We were able to identify phonon modes in which the motion of core atoms is significant when it is compared with motion of atoms on the nanowire's shell. The thermal conductivity in these nanostructures depends on the nanowire's diameter and on the Si atoms concentration.
Download or read book Modeling Energy Transport in Nanostructures written by Arvind Pattamatta and published by LAP Lambert Academic Publishing. This book was released on 2013 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat transfer in nanostructures differ significantly from that in the bulk materials since the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of the nanostructures. Nanostructure materials hold the promise of novel phenomena, properties, and functions in the areas of thermal management and energy conversion. Three important topics are studied with respect to energy transport in nanostructure materials for micro/nano electronic and thermoelectric applications: 1) the role of nanocomposites in improving the thermal efficiency of thermoelectric devices, 2) the interfacial thermal resistance for the semiconductor/metal contacts in thermoelectric devices and for metallic interconnects in micro/nano electronic devices, 3) the interaction between the energy carriers namely electrons/carriers with phonons which lead to a significant non-equilibrium at the semiconductor-metal contacts.
Download or read book Molecular Dynamics Simulation of Thermal Energy Transport Across Material Interfaces written by Tengfei Luo and published by . This book was released on 2009 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: Both ab-initio and classical molecular dynamics (MD) were used to study the thermal energy transport phenomena across nano-scale material interfaces. Thermal equilibration in semiconductor ultra-thin layered superlattices was simulated by ab-initio MD with density functional theory (OFT). Equilibrium MD (EMD) and Non-equilibrium MD (NEMD) simulations were performed on Au-SAM (self-assembly monolayer)-Au junctions with alkanedithiols being the SAM molecules. The in-plane thermal conductivities were calculated using EMD with Green-Kubo method. The out-of-plane thermal conductances were calculated in both EMD and NEMD simulations. Au substrate thickness effect, temperature effect, simulated normal pressure effect, molecular chain length effect, molecule coverage effect and molecule-substrate bonding strength effect on thermal conductivity/conductance were studied. Vibration density of states (VDOS) was calculated, and the mechanism of thermal energy transport across the material junctions was analyzed. The calculated thermal conductance at high temperatures agrees well with available experimental data. The temperature dependence of thermal conductance has a similar trend to experimental observations. SAM molecular coverage was found to be important on the interfacial thermal conductance. Analysis of the junction response to a heat pulse showed that the Au-SAM interface resistance was much larger than the substrate and SAM resistances. The results showed that the Au-SAM interface resistance dominated thermal energy transport across the junction The DFT ab-initio method was used to study the bondings of thiols on As-terminated GaAs (001) surfaces. As-S interactions were simulated by the Morse potential, and the parameters were fitted to an energy hypersurface obtained from DFT calculations. NEMD simulations were then performed on GaAs-SAM-GaAs junctions to study thermal energy transport across thiol-GaAs interfaces. NEMD simulations were also carried out to study thermal energy transport across different graphene-polymer interfaces. The results of this study will be useful for the current molecular electronics industry in which thermal dissipation is a critical problem to be resolved. It is concluded that the interfacial resistance is the barrier for thermal transport across molecule-solid junctions. As a result, methods to facilitate thermal transport across the interfaces, such as depositing denser SAM, forming stronger molecule-solid bonds, choosing materials with better vibration coupling, are to be considered in the emerging technology of the manufacturing of molecular electronics.
