Download or read book Nanoscale Hotspots Due to Nonequilibrium Thermal Transport written by Sanjiv Sinha and published by . This book was released on 2004 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experimental and modeling efforts have been directed towards the issue of temperature localization and hotspot formation in the vicinity of nanoscale heat generating devices. The nonequilibrium transport conditions which develop around these nanoscale devices results in elevated temperatures near the heat source which can not be predicted by continuum diffusion theory. Efforts to determine the severity of this temperature localization phenomena in silicon devices near and above room temperature are of technological importance to the development of microelectronics and other nanotechnologies. In this work, we have developed a new modeling tool in order to explore the magnitude of the additional thermal resistance which forms around nanoscale hotspots from temperatures of 100-1000K. The models are based on a two fluid approximation in which thermal energy is transferred between ''stationary'' optical phonons and fast propagating acoustic phonon modes. The results of the model have shown excellent agreement with experimental results of localized hotspots in silicon at lower temperatures. The model predicts that the effect of added thermal resistance due to the nonequilibrium phonon distribution is greatest at lower temperatures, but is maintained out to temperatures of 1000K. The resistance predicted by the numerical code can be easily integrated with continuum models in order to predict the temperature distribution around nanoscale heat sources with improved accuracy. Additional research efforts also focused on the measurements of the thermal resistance of silicon thin films at higher temperatures, with a focus on polycrystalline silicon. This work was intended to provide much needed experimental data on the thermal transport properties for micro and nanoscale devices built with this material. Initial experiments have shown that the exposure of polycrystalline silicon to high temperatures may induce recrystallization and radically increase the thermal transport properties at room temperature. In addition, the defect density was observed to play a major role in the rate of change in thermal resistivity as a function of temperature.
Download or read book The Non Equilibrium Green s Function Method for Nanoscale Device Simulation written by Mahdi Pourfath and published by Springer. This book was released on 2014-07-05 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: For modeling the transport of carriers in nanoscale devices, a Green-function formalism is the most accurate approach. Due to the complexity of the formalism, one should have a deep understanding of the underlying principles and use smart approximations and numerical methods for solving the kinetic equations at a reasonable computational time. In this book the required concepts from quantum and statistical mechanics and numerical methods for calculating Green functions are presented. The Green function is studied in detail for systems both under equilibrium and under nonequilibrium conditions. Because the formalism enables rigorous modeling of different scattering mechanisms in terms of self-energies, but an exact evaluation of self-energies for realistic systems is not possible, their approximation and inclusion in the quantum kinetic equations of the Green functions are elaborated. All the elements of the kinetic equations, which are the device Hamiltonian, contact self-energies and scattering self-energies, are examined and efficient methods for their evaluation are explained. Finally, the application of these methods to study novel electronic devices such as nanotubes, graphene, Si-nanowires and low-dimensional thermoelectric devices and photodetectors are discussed.
Download or read book Dynamical Analysis of Non Fourier Heat Conduction and Its Application in Nanosystems written by Yuan Dong and published by Springer. This book was released on 2015-10-14 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis studies the general heat conduction law, irreversible thermodynamics and the size effect of thermal conductivity exhibited in nanosystems from the perspective of recently developed thermomass theory. The derivation bridges the microscopic phonon Boltzmann equation and macroscopic continuum mechanics. Key concepts such as entropy production, temperature and the Onsager reciprocal relation are revisited in the case of non-Fourier heat conduction. Lastly, useful expressions are extracted from the picture of phonon gas dynamics and are used to successfully predict effective thermal conductivity in nanosystems.
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 Quantifying Nanoscale Carrier Diffusion with Ultrafast Optical and Photocurrent Microscopy written by Alexander Block and published by . This book was released on 2020 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat transport in solids is one of the oldest problems in physics, dating back to the earliest formulations of thermodynamics. The classical laws of heat conduction are valid as long as the observed time and length scales are larger than the relaxation time and mean free path of the underlying microscopic heat carriers, such as electrons and phonons. With the advent of ultrafast lasers and nanoscale systems these regimes can now be surpassed and new refined models of heat transport are needed. In particular, the interaction of ultrashort light pulses with matter can excite electrons to high temperatures, leading to a local non-equilibrium of electrons and phonons. Under these conditions, also the transport properties of the carriers are altered.So far, these effects have typically been studied in the time domain. The cooling of photo-excited hot electrons has been studied both in metals as well as novel 2D materials, such as graphene. However, due to a lack of spatio-temporal resolution, it has not been possible to distinguish the effects of hot-electron diffusion from other cooling mechanisms, such as electron-phonon coupling.In this thesis, I directly track such ultrafast heat and carrier diffusion in space and time with ultrafast microscopy. By using the recently developed technique of probe-beam-scanning transient-absorption microscopy on thin gold films I directly resolve, for the first time, a transition from hot-electron diffusion to phonon-limited diffusion on the picosecond timescale. I support the understanding of these complex dynamics by theoretical modeling of the thermo-optical response based on a two-temperature model.I apply the same technique to study hot carrier diffusion in atomically thin monolayer graphene. By comparing differently prepared samples, I study the strong influence of external parameters, such as production type, substrate, and environment on carrier diffusion. Finally, I study hot carrier diffusion in exfoliated and encapsulated graphene devices with a novel technique of ultrafast spatio-temporal photocurrent microscopy based on the photothermoelectric effect. I extract diffusion dynamics for electrically characterized samples with the help of theoretical spatio-temporal modeling, thereby testing the fundamental relationship between electrical and thermal carrier transport.The precise quantification of ultrafast and nanoscale carrier transport with these state-of-the-art techniques leads to a broader understanding of non-equilibrium dynamics and could ultimately help the design, optimization, and heat management of the next generation of ultra-compact (opto-) electronic devices, such as solar cells, photodetectors, or integrated circuits.
Download or read book 21st Century Nanoscience A Handbook written by Klaus D. Sattler and published by CRC Press. This book was released on 2019-11-21 with total page 371 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 Nanoscale Energy Transport and Conversion written by Gang Chen and published by Oxford University Press. This book was released on 2005-03-03 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a graduate level textbook in nanoscale heat transfer and energy conversion that can also be used as a reference for researchers in the developing field of nanoengineering. It provides a comprehensive overview of microscale heat transfer, focusing on thermal energy storage and transport. Chen broadens the readership by incorporating results from related disciplines, from the point of view of thermal energy storage and transport, and presents related topics on the transport of electrons, phonons, photons, and molecules. This book is part of the MIT-Pappalardo Series in Mechanical Engineering.
Download or read book Nano Microscale Heat Transfer written by Zhuomin M. Zhang and published by Springer Nature. This book was released on 2020-06-23 with total page 780 pages. Available in PDF, EPUB and Kindle. Book excerpt: This substantially updated and augmented second edition adds over 200 pages of text covering and an array of newer developments in nanoscale thermal transport. In Nano/Microscale Heat Transfer, 2nd edition, Dr. Zhang expands his classroom-proven text to incorporate thermal conductivity spectroscopy, time-domain and frequency-domain thermoreflectance techniques, quantum size effect on specific heat, coherent phonon, minimum thermal conductivity, interface thermal conductance, thermal interface materials, 2D sheet materials and their unique thermal properties, soft materials, first-principles simulation, hyperbolic metamaterials, magnetic polaritons, and new near-field radiation experiments and numerical simulations. Informed by over 12 years use, the author’s research experience, and feedback from teaching faculty, the book has been reorganized in many sections and enriched with more examples and homework problems. Solutions for selected problems are also available to qualified faculty via a password-protected website.• Substantially updates and augments the widely adopted original edition, adding over 200 pages and many new illustrations;• Incorporates student and faculty feedback from a decade of classroom use;• Elucidates concepts explained with many examples and illustrations;• Supports student application of theory with 300 homework problems;• Maximizes reader understanding of micro/nanoscale thermophysical properties and processes and how to apply them to thermal science and engineering;• Features MATLAB codes for working with size and temperature effects on thermal conductivity, specific heat of nanostructures, thin-film optics, RCWA, and near-field radiation.
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 188 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 Non classical Thermal Transport and Phase Change at the Nanoscale written by Marc Calvo Schwarzwälder and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: For 200 years, Fourier's law has been used to describe heat transfer with excellent results. However, as technology advances, more and more situations arise where heat conduction is not well described by the classical equations. Examples are applications with extremely short time scales such as ultra fast laser heating, or very small length scales such as the heat conduction through nanowires or nanostructures in general. In this thesis we investigate alternative models which aim to correctly describe the non-classical effects that appear in extreme situations and which Fourier's law fails to describe. A popular approach is the Guyer-Krumhansl equation and the framework of phonon hydrodynamics. This formalism is particularly appealing from a mathematical point of view since it is analogous to the Navier-Stokes equations of fluid mechanics, and from a physical point of view, since it is able to describe the physics in a simple and elegant way. In the first part of the thesis we use phonon hydrodynamics to predict the size-dependent thermal conductivity observed experimentally in nanostructures such as nanowires or thin films. In particular, we show that the Guyer-Krumhansl equation is suitable to capture the dependence of the thermal conductivity on the size of the physical system under consider- ation. During the modelling process we use the analogy with fluids to incorporate a slip boundary condition with a slip coefficient that depends on the ratio of the phonon mean free path to the characteristic size of the system. With only one fitting parameter we are able to accurately reproduce experimental observations corresponding to nanowires and nanorods of different sizes. The second part of the thesis consists of studying the effect of the non-classical fea- tures on melting and solidification processes. We consider different extensions and in- corporate them into the mathematical description of a solidification process in a simple, one-dimensional geometry. In chapter 5 we employ an effective Fourier law which replaces the original thermal conductivity by a size-dependent expression that accounts for non-local effects. In chapter 6 we use the Maxwell-Cattaneo and the Guyer-Krumhansl equations to formulate the Maxwell-Cattaneo-Stefan and the Guyer-Krumhansl-Stefan problems respec- tively. After performing a detailed asymptotic analysis we are able to reduce both models to a system of two ordinary differential equations and obtain excellent agreement with the cor- responding numerical solutions. In situations near Fourier resonance, which is a particular case where non-classical effects in the Guyer-Krumhansl model cancel each other out, the solidification kinetics are very similar to those described by the classical model. However, in this case we see that non-classical effects are still observable in the evolution of the heat flux through the solid, which suggests that this is a quantity which is more convenient to determine the presence of these effects in phase change processes.
Download or read book Nonequilibrium Carrier Dynamics in Semiconductors written by Marco Saraniti and published by Springer Science & Business Media. This book was released on 2007-12-14 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Nonequilibrium Carrier Dynamics in Semiconductors" is a well-established, specialist conference, held every two years, covering a range of topics of current interest to R&D in semiconductor physics/materials, optoelectronics, nanotechnology, quantum information processing. Papers accepted for publication are selected and peer-reviewed by members of the Program Committee during the conference to ensure both rapid and high-quality processing.
Download or read book MODELING ENERGY TRANSPORT IN NANOSTRUCTURES written by Arvind Pattamatta and published by . This book was released on 2009 with total page 225 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. Example of thermal management in micro/nano electronic devices is the use of efficient nanostructured materials to alleviate `hot spots' in integrated circuits. Examples in the manipulation of heat flow and energy conversion include nanostructures for thermoelectric energy conversion, thermophotovoltaic power generation, and data storage. One of the major challenges in Metal-Oxide Field Effect Transistor (MOSFET) devices is to study the `hot spot' generation by accurately modeling the carrier-optical phonon-acoustic phonon interactions.^Prediction of hotspot temperature and position in MOSFET devices is necessary for improving thermal design and reliability of micro/nano electronic devices. Thermoelectric properties are among the properties that may drastically change at nanoscale. The efficiency of thermoelectric energy conversion in a material is measured by a non-dimensional figure of merit (ZT).^During the last decade, advances have been made in increasing ZT using nanostructures. 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. This talk aims to focus on these three important topics. The first topic is addressed by modeling the thermal transport in 2-D and 3-D nanocomposites. The Boltzmann transport equation (BTE) for the phonon intensity is solved in conjunction with suitable boundary and interface treatment.^Unlike in bulk composites, the results show a strong dependence of thermal conductivity, temperature, and heat flux on the wire size, wire atomic ratio, and interface specularity parameter. The second topic is addressed through a computational study for modeling the interfacial thermal resistance in carbon nanotube (CNT) contacts. A detailed parametric study is conducted by varying the dimensions of the CNT. The results of this study are compared with experimental data and the theory developed for nanoscale contacts. The third topic is addressed by modeling the non-equilibrium between energy carriers in metals and semiconductors. The Boltzmann transport model (BTM) has been introduced to study the electron-phonon non-equilibrium due to short pulsed laser interaction with thin gold and silicon films.^A three stage Runge Kutta (RK) time stepping and a higher order Discontinuous Galerkin (DG) scheme using two Legendre basis functions are implemented for temporal and spatial discretization of the BTM. A parametric study is conducted by varying the laser parameters and studying their effect on electron/carrier and phonon thermal characteristics.
Download or read book Annual Review of Heat Transfer written by and published by . This book was released on 2005 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Non Fourier Heat Conduction written by Alexander I. Zhmakin and published by Springer Nature. This book was released on 2023-07-01 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a broad and well-structured overview of various non-Fourier heat conduction models. The classical Fourier heat conduction model is valid for most macroscopic problems. However, it fails when the wave nature of the heat propagation becomes dominant and memory or non-local spatial effects become significant; e.g., during ultrafast heating, heat transfer at the nanoscale, in granular and porous materials, at extremely high values of the heat flux, or in heat transfer in biological tissues. The book looks at numerous non-Fourier heat conduction models that incorporate time non-locality for materials with memory, such as hereditary materials, including fractional hereditary materials, and/or spatial non-locality, i.e. materials with a non-homogeneous inner structure. Beginning with an introduction to classical transport theory, including phase-lag, phonon, and thermomass models, the book then looks at various aspects of relativistic and quantum transport, including approaches based on the Landauer formalism as well as the Green-Kubo theory of linear response. Featuring an appendix that provides an introduction to methods in fractional calculus, this book is a valuable resource for any researcher interested in theoretical and numerical aspects of complex, non-trivial heat conduction problems.
Download or read book Modeling Self Heating Effects in Nanoscale Devices written by Katerina Raleva and published by Morgan & Claypool Publishers. This book was released on 2017-09-13 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is generally acknowledged that modeling and simulation are preferred alternatives to trial and error approaches to semiconductor fabrication in the present environment, where the cost of process runs and associated mask sets is increasing exponentially with successive technology nodes. Hence, accurate physical device simulation tools are essential to accurately predict device and circuit performance. Accurate thermal modelling and the design of microelectronic devices and thin film structures at the micro- and nanoscales poses a challenge to electrical engineers who are less familiar with the basic concepts and ideas in sub-continuum heat transport. This book aims to bridge that gap. Efficient heat removal methods are necessary to increase device performance and device reliability. The authors provide readers with a combination of nanoscale experimental techniques and accurate modelling methods that must be employed in order to determine a device's temperature profile.
Download or read book Special Section on Thermal Transport in Nanoscale Semiconductors written by Kornelius Nielsch and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nanofluidics written by Efstathios E. (Stathis) Michaelides and published by Springer. This book was released on 2014-05-19 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume offers a comprehensive examination of the subject of heat and mass transfer with nanofluids as well as a critical review of the past and recent research projects in this area. Emphasis is placed on the fundamentals of the transport processes using particle-fluid suspensions, such as nanofluids. The nanofluid research is examined and presented in a holistic way using a great deal of our experience with the subjects of continuum mechanics, statistical thermodynamics, and non-equilibrium thermodynamics of transport processes. Using a thorough database, the experimental, analytical, and numerical advances of recent research in nanofluids are critically examined and connected to past research with medium and fine particles as well as to functional engineering systems. Promising applications and technological issues of heat/mass transfer system design with nanofluids are also discussed. This book also: Provides a deep scientific analysis of nanofluids using classical thermodynamics and statistical thermodynamics to explain and interpret experimental observations Presents the theory and experimental results for both thermodynamic and transport properties Examines all transport properties and transport processes as well as their relationships through the pertinent macroscopic coefficients Combines recent knowledge pertaining to nanofluids with the previous fifty years of research on particulate flows, including research on transient flow and heat transfer of particulate suspensions Conducts an holistic examination of the material from more than 500 archival publications
