Download or read book Observation and Manipulation of the Wave Nature of Phonon Thermal Transport Through Superlattices written by Maria Nickolayevna Luckyanova and published by . This book was released on 2015 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the scale of electronic, photonic, and energy harvesting devices has shrunk, the importance of understanding nanoscale thermal transport has grown. In this thesis, we investigate thermal transport through superlattices (SLs), periodic layers of thin films, to better understand thermal conduction at these small scales. The classical picture of nanoscale thermal transport invokes a picture of diffusive scattering of phonons, or lattice vibrations, at the interfaces and boundaries in structures. This picture has been used to explain experimental thermal transport results for a wide variety of nanostructures. Despite the omnipresence of this particle-transport picture of phonon heat conduction, the community has continuously sought an experimental demonstration of the wave regime of thermal transport in nanostructures. In this thesis, we report the first experimental observations of the regimes of coherent phonon transport and phonon localization in thermal conduction through nanostructures. First, in order to better understand thermal transport through SLs, we present measurements of anisotropic thermal conductivity in the same GaAs/AlAs SLs using two different optical techniques, time-domain thermoreflectance (TDTR) for cross-plane measurements, and transient thermal grating (TTG) for in-plane measurements. The results of this study lend insight into the role of interface scattering, previously understood to be the dominant scattering mechanism in these structures, in SLs. The experimentally measured thermal conductivities are compared to results from first principles simulations, and the agreement between the two helps to validate atomistic simulation techniques of transport through SLs. The role of coherent phonon transport is explored by using the TDTR technique to measure the thermal conductivities of SLs with the same period thicknesses but varying numbers of periods. This experimental approach is a departure from traditional studies of SLs where period thicknesses are varied while the SL is grown to be thermally thick. This shift in the experimental paradigm allows us to explore previously elusive phenomena in nanoscale thermal transport. Combined with first principles and Green's functions simulations, the results of these experiments are the first experimental observation of coherent phonon transport through SLs. Finally, experiments on GaAs/AlAs SLs with varying concentrations of ErAs nanodots at the interfaces show the ability to destroy this phonon coherence. The thermal conductivities of such SLs with constant period thicknesses and varying numbers of periods show an overall reduction in thermal conductivity with increasing ErAs concentration. In addition, at low temperatures samples with ErAs at the interfaces show a maximum in thermal conductivity with shorter sample length and then a drop-off for longer samples. These results are signatures of phonon localization, a previously unobserved thermal transport phenomenon.
Download or read book Detecting Coherent Phonon Wave Effects in Superlattices Using Time domain Thermoreflectance written by Maria Nickolayevna Luckyanova and published by . This book was released on 2012 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superlattices (SLs), structures consisting of periodic layers of thin films of several angstroms to tens of nanometers thick, have unique electrical and thermal properties that make them well suited for applications in optoelectronics and as fundamental learning tools in the realm of thermoelectrics. One unique characteristic of SLs is their low thermal conductivity compared to a bulk material with the same molecular composition. This property has given rise to extensive theoretical and experimental investigations regarding thermal transport through SLs. The different thermal transport characteristics have been studied in the context of various transport regimes. In this thesis, an experimental investigation of thermal transport in the coherent regime through a SL is presented. The trend in thermal conductivity that can be expected if such coherent wave effects exist is derived from the Landauer-Biittiker formalism, which treats energy transport as a transmission process. The frequency-dependent transmission probability for phonons through the SL is found via an application of the transfer matrix method (TMM). The calculations show that the integral effect of the buildup of phonon stopbands in the SL is minimal. Thus, if coherent wave effects are present, the conductance of the SL is nearly constant as the number of periods is increased, and the thermal conductivity, which is the product of the conductance and the total thickness of the SL, increases linearly with number of periods. To test the predictions, five GaAs/AlAs SLs with one, three, five, seven, and nine periods of one layer of GaAs of 12 nm thickness, and one layer of AlAs of 12 nm thickness are grown using MOCVD. The thermal conductivities of the SLs are measured using a transient thermoreflectance (TTR) technique at temperatures ranging from 30K to 300K. The results are the first-ever experimental evidence for the presence of coherent wave effects in heat transport through SLs.
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 Manipulation of Thermal Phonons written by Chung-Hao Hsu and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing materials that can conduct electricity easily, but block the motion of phonons is necessary in the applications of thermoelectric devices, which can generate electricity from temperature differences. In converse, a key requirement as chips get faster is to obtain better ways to dissipate heat. Controlling heat transfer in these crystalline materials devices -- such as silicon -- is important. The heat is actually the motion or vibration of atoms known as phonons. Finding ways to manipulate the behavior of phonons is crucial for both energy applications and the cooling of integrated circuits. A novel class of artificially periodic structured materials -- phononic crystals -- might make manipulation of thermal phonons possible. In many fields of physical sciences and engineering, acoustic wave propagation in solids attracts many researchers. Wave propagation phenomena can be analyzed by mathematically solving the acoustic wave equation. However, wave propagation in inhomogeneous media with various geometric structures is too complex to find an exact solution. Hence, the Finite Difference Time Domain method is developed to investigate these complicated problems. In this work, the Finite-Difference Time-Domain formula is derived from acoustic wave equations based on the Taylor's expansion. The numerical dispersion and stability problems are analyzed. In addition, the convergence conditions of numerical acoustic wave are stated. Based on the periodicity of phononic crystal, the Bloch's theorem is applied to fulfill the periodic boundary condition of the FDTD method. Then a wide-band input signal is used to excite various acoustic waves with different frequencies. In the beginning of the calculation process, the wave vector is chosen and fixed. By means of recording the displacement field and taking the Fourier transformation, we can obtain the eigenmodes from the resonance peaks of the spectrum and draw the dispersion relation curve of acoustic waves. With the large investment in silicon nanofabrication techniques, this makes tungsten/silicon phononic crystal a particularly attractive platform for manipulating thermal phonons. Phononic crystal makes use of the fundamental properties of waves to create band gap over which there can be no propagation of acoustic waves in the crystal. This crystal can be applied to deterministically manipulate the phonon dispersion curve affected by different crystal structures and to modify the phonon thermal conductivity accordingly. We can expect this unique metamaterial is a promising route to creating unprecedented thermal properties for highly-efficient energy harvesting and thermoelectric cooling. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149346
Download or read book Phonon Properties in Superlattices written by Samuel C. Huberman and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavity Optomechanics written by Markus Aspelmeyer and published by Springer. This book was released on 2014-07-05 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last few years cavity-optomechanics has emerged as a new field of research. This highly interdisciplinary field studies the interaction between micro and nano mechanical systems and light. Possible applications range from novel high-bandwidth mechanical sensing devices through the generation of squeezed optical or mechanical states to even tests of quantum theory itself. This is one of the first books in this relatively young field. It is aimed at scientists, engineers and students who want to obtain a concise introduction to the state of the art in the field of cavity optomechanics. It is valuable to researchers in nano science, quantum optics, quantum information, gravitational wave detection and other cutting edge fields. Possible applications include biological sensing, frequency comb applications, silicon photonics etc. The technical content will be accessible to those who have familiarity with basic undergraduate physics.
Download or read book Introduction to Thermoelectricity written by H. Julian Goldsmid and published by Springer Science & Business Media. This book was released on 2009-10-03 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduction to Thermoelectricity is the latest work by Professor Julian Goldsmid drawing on his 55 years experience in the field. The theory of the thermoelectric and related phenomena is presented in sufficient detail to enable researchers to understand their observations and develop improved thermoelectric materials. The methods for the selection of materials and their improvement are discussed. Thermoelectric materials for use in refrigeration and electrical generation are reviewed. Experimental techniques for the measurement of properties and for the production of thermoelements are described. Special emphasis is placed on nanotechnology which promises to yield great improvements in the efficiency of thermoelectric devices. Chapters are also devoted to transverse thermoelectric effects and thermionic energy conversion, both techniques offering the promise of important applications in the future.
Download or read book Multilayer Thin Films written by Sukumar Basu and published by BoD – Books on Demand. This book was released on 2020-01-15 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, "Multilayer Thin Films-Versatile Applications for Materials Engineering", includes thirteen chapters related to the preparations, characterizations, and applications in the modern research of materials engineering. The evaluation of nanomaterials in the form of different shapes, sizes, and volumes needed for utilization in different kinds of gadgets and devices. Since the recently developed two-dimensional carbon materials are proving to be immensely important for new configurations in the miniature scale in the modern technology, it is imperative to innovate various atomic and molecular arrangements for the modifications of structural properties. Of late, graphene and graphene-related derivatives have been proven as the most versatile two-dimensional nanomaterials with superb mechanical, electrical, electronic, optical, and magnetic properties. To understand the in-depth technology, an effort has been made to explain the basics of nano dimensional materials. The importance of nano particles in various aspects of nano technology is clearly indicated. There is more than one chapter describing the use of nanomaterials as sensors. In this volume, an effort has been made to clarify the use of such materials from non-conductor to highly conducting species. It is expected that this book will be useful to the postgraduate and research students as this is a multidisciplinary subject.
Download or read book Thermoelectric Nanomaterials written by Kunihito Koumoto and published by Springer Science & Business Media. This book was released on 2013-07-20 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presently, there is an intense race throughout the world to develop good enough thermoelectric materials which can be used in wide scale applications. This book focuses comprehensively on very recent up-to-date breakthroughs in thermoelectrics utilizing nanomaterials and methods based in nanoscience. Importantly, it provides the readers with methodology and concepts utilizing atomic scale and nanoscale materials design (such as superlattice structuring, atomic network structuring and properties control, electron correlation design, low dimensionality, nanostructuring, etc.). Furthermore, also indicates the applications of thermoelectrics expected for the large emerging energy market. This book has a wide appeal and application value for anyone being interested in state-of-the-art thermoelectrics and/or actual viable applications in nanotechnology.
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 Fundamentals of Semiconductors written by Peter YU and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 651 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excellent bridge between general solid-state physics textbook and research articles packed with providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors "The most striking feature of the book is its modern outlook ... provides a wonderful foundation. The most wonderful feature is its efficient style of exposition ... an excellent book." Physics Today "Presents the theoretical derivations carefully and in detail and gives thorough discussions of the experimental results it presents. This makes it an excellent textbook both for learners and for more experienced researchers wishing to check facts. I have enjoyed reading it and strongly recommend it as a text for anyone working with semiconductors ... I know of no better text ... I am sure most semiconductor physicists will find this book useful and I recommend it to them." Contemporary Physics Offers much new material: an extensive appendix about the important and by now well-established, deep center known as the DX center, additional problems and the solutions to over fifty of the problems at the end of the various chapters.
Download or read book Physics of Surfaces and Interfaces written by Harald Ibach and published by Springer Science & Business Media. This book was released on 2006-11-18 with total page 653 pages. Available in PDF, EPUB and Kindle. Book excerpt: This graduate-level textbook covers the major developments in surface sciences of recent decades, from experimental tricks and basic techniques to the latest experimental methods and theoretical understanding. It is unique in its attempt to treat the physics of surfaces, thin films and interfaces, surface chemistry, thermodynamics, statistical physics and the physics of the solid/electrolyte interface in an integral manner, rather than in separate compartments. It is designed as a handbook for the researcher as well as a study-text for graduate students. Written explanations are supported by 350 graphs and illustrations.
Download or read book Electrons and Phonons written by J.M. Ziman and published by Oxford University Press. This book was released on 2001-02 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a classic text of its time in condensed matter physics.
Download or read book Semiconductor Nanowires written by J Arbiol and published by Elsevier. This book was released on 2015-03-31 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanowires promise to provide the building blocks for a new generation of nanoscale electronic and optoelectronic devices. Semiconductor Nanowires: Materials, Synthesis, Characterization and Applications covers advanced materials for nanowires, the growth and synthesis of semiconductor nanowires—including methods such as solution growth, MOVPE, MBE, and self-organization. Characterizing the properties of semiconductor nanowires is covered in chapters describing studies using TEM, SPM, and Raman scattering. Applications of semiconductor nanowires are discussed in chapters focusing on solar cells, battery electrodes, sensors, optoelectronics and biology. Explores a selection of advanced materials for semiconductor nanowires Outlines key techniques for the property assessment and characterization of semiconductor nanowires Covers a broad range of applications across a number of fields
Download or read book Theoretical Thermotics written by Ji-Ping Huang and published by Springer Nature. This book was released on 2019-12-31 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on theoretical thermotics, the theory of transformation thermotics and its extended theories for the active control of macroscopic thermal phenomena of artificial systems, which is in sharp contrast to classical thermodynamics comprising the four thermodynamic laws for the passive description of macroscopic thermal phenomena of natural systems. The book covers the basic concepts and mathematical methods, which are necessary to understand thermal problems extensively investigated in physics, but also in other disciplines of engineering and materials. The analyses rely on models solved by analytical techniques accompanied with computer simulations and laboratory experiments. This book serves both as a reference work for senior researchers and a study text for zero beginners.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phononic Crystals written by Abdelkrim Khelif and published by Springer. This book was released on 2015-07-28 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an in-depth analysis as well as an overview of phononic crystals. This book discusses numerous techniques for the analysis of phononic crystals and covers, among other material, sonic and ultrasonic structures, hypersonic planar structures and their characterization, and novel applications of phononic crystals. This is an ideal book for those working with micro and nanotechnology, MEMS (microelectromechanical systems), and acoustic devices. This book also: Presents an introduction to the fundamentals and properties of phononic crystals Covers simulation techniques for the analysis of phononic crystals Discusses sonic and ultrasonic, hypersonic and planar, and three-dimensional phononic crystal structures Illustrates how phononic crystal structures are being deployed in communication systems and sensing systems
