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 Manipulation Thermal Phonons written by and published by . This book was released on 2011 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Manipulating Thermal Phonons written by and published by . This book was released on 2012 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Phonon Manipulation with Phononic Crystals written by and published by . This book was released on 2012 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, we demonstrated engineered modification of propagation of thermal phonons, i.e. at THz frequencies, using phononic crystals. This work combined theoretical work at Sandia National Laboratories, the University of New Mexico, the University of Colorado Boulder, and Carnegie Mellon University; the MESA fabrication facilities at Sandia; and the microfabrication facilities at UNM to produce world-leading control of phonon propagation in silicon at frequencies up to 3 THz. These efforts culminated in a dramatic reduction in the thermal conductivity of silicon using phononic crystals by a factor of almost 30 as compared with the bulk value, and about 6 as compared with an unpatterned slab of the same thickness. This work represents a revolutionary advance in the engineering of thermoelectric materials for optimal, high-ZT performance. We have demonstrated the significant reduction of the thermal conductivity of silicon using phononic crystal structuring using MEMS-compatible fabrication techniques and in a planar platform that is amenable to integration with typical microelectronic systems. The measured reduction in thermal conductivity as compared to bulk silicon was about a factor of 20 in the cross-plane direction [26], and a factor of 6 in the in-plane direction. Since the electrical conductivity was only reduced by a corresponding factor of about 3 due to the removal of conductive material (i.e., porosity), and the Seebeck coefficient should remain constant as an intrinsic material property, this corresponds to an effective enhancement in ZT by a factor of 2. Given the number of papers in literature devoted to only a small, incremental change in ZT, the ability to boost the ZT of a material by a factor of 2 simply by reducing thermal conductivity is groundbreaking. The results in this work were obtained using silicon, a material that has benefitted from enormous interest in the microelectronics industry and that has a fairly large thermoelectric power factor. In addition, the techniques and scientific understanding developed in the research can be applied to a wide range of materials, with the caveat that the thermal conductivity of such a material be dominated by phonon, rather than electron, transport. In particular, this includes several thermoelectric materials with attractive properties at elevated temperatures (i.e., greater than room temperature), such as silicon germanium and silicon carbide. It is reasonable that phononic crystal patterning could be used for high-temperature thermoelectric devices using such materials, with applications in energy scavenging via waste-heat recovery and thermoelectric cooling for high-performance microelectronic circuits. The only part of the ZT picture missing in this work was the experimental measurement of the Seebeck coefficient of our phononic crystal devices. While a first-order approximation indicates that the Seebeck coefficient should not change significantly from that of bulk silicon, we were not able to actually verify this assumption within the timeframe of the project. Additionally, with regards to future high-temperature applications of this technology, we plan to measure the thermal conductivity reduction factor of our phononic crystals as elevated temperatures to confirm that it does not diminish, given that the nominal thermal conductivity of most semiconductors, including silicon, decreases with temperature above room temperature. We hope to have the opportunity to address these concerns and further advance the state-of-the-art of thermoelectric materials in future projects.

Download or read book Nanosources and Manipulation of Atoms Under High Fields and Temperatures Applications written by Vu Thien Binh and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the NATO-Advanced Research Workshop (ARW) "Manipulation of atoms under high fields and temperatures: Applications", sponsored by the NATO Scientific Affairs Division, Special Programme on Nanoscale Science. This ARW took place in Summer '92, in the pleasant surroundings of the Hotel des Thermes at Charbonnieres les Bains -Lyon, France. Gathering some fifty experts from different fields, the ARW provided an opportunity to review the basic principles and to highlight the progress made during the last few years on the nanosources and the interactions between atomic-scale probes and samples. The motivation is to use the novel properties attached to the atomic dimensions to develop nanoscale technologies. The perception of the atomic-scale world has greatly changed since the discovery and development, in the early 80's, of Scanning Tunneling Microscopy (STM) by Binnig and Rohrer. Beyond the observation of individual atoms, which is now routine, the concept of playing with atoms has become commonplace. This has lead to the fashioning of tools at the atomic scale, to the deposition, the displacement and the creation of atomic structures and also to the knowledge of interactions and contacts between atoms. Nanotips ending with a single atom are sources of ultra-fine charged beams. They can be unique tools for high resolution observations, for micro fabrications by micro-machining and deposition at a scale not previously attainable, with a working distance less stringent than with STM devices.

Download or read book Acoustic Metamaterials and Phononic Crystals written by Pierre A. Deymier and published by Springer Science & Business Media. This book was released on 2013-01-13 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive book presents all aspects of acoustic metamaterials and phononic crystals. The emphasis is on acoustic wave propagation phenomena at interfaces such as refraction, especially unusual refractive properties and negative refraction. A thorough discussion of the mechanisms leading to such refractive phenomena includes local resonances in metamaterials and scattering in phononic crystals.

Download or read book Physical Origins Implications and Applications of Tailored Phononic Bandgaps written by and published by . This book was released on 2009 with total page 30 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 Beyond CMOS Nanodevices 1 written by Francis Balestra and published by John Wiley & Sons. This book was released on 2014-06-02 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a comprehensive review of the state-of-the-art in innovative Beyond-CMOS nanodevices for developing novel functionalities, logic and memories dedicated to researchers, engineers and students. It particularly focuses on the interest of nanostructures and nanodevices (nanowires, small slope switches, 2D layers, nanostructured materials, etc.) for advanced More than Moore (RF-nanosensors-energy harvesters, on-chip electronic cooling, etc.) and Beyond-CMOS logic and memories applications.

Download or read book Thermoplasmonics written by Guillaume Baffou and published by Cambridge University Press. This book was released on 2017-10-19 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasmonics is an important branch of optics concerned with the interaction of metals with light. Under appropriate illumination, metal nanoparticles can exhibit enhanced light absorption, becoming nanosources of heat that can be precisely controlled. This book provides an overview of the exciting new field of thermoplasmonics and a detailed discussion of its theoretical underpinning in nanophotonics. This topic has developed rapidly in the last decade, and is now a highly-active area of research due to countless applications in nanoengineering and nanomedicine. These important applications include photothermal cancer therapy, drug and gene delivery, nanochemistry and photothermal imaging. This timely and self-contained text is suited to all researchers and graduate students working in plasmonics, nano-optics and thermal-induced processes at the nanoscale.

Download or read book Phonon Scattering in Condensed Matter written by Humphrey Maris and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Third International Conference on Phonon Scattering in Condensed Matter was held at Brown University, Providence, Rhode Island from August 28-31, 1979. The previous conferences in this series were held at Nottingham in 1975, and in France at Paris and Ste Maxime in 1972. Until about 15 years ago phonon scattering was studied almost exclusively by measurements of thermal conductivity. This approach has the severe limitation that the result obtained for the phonon scattering rate is actually the average of the scattering for all of the phonons in the sample. Thus, no distinction can be made between phonons of different polarization, direction of propagation, or energy. During the 1960's several significant developments occurred. The most important of these was the application by Von Gutfeld and Nethercot of the "heat-pulse" method, previously used only in liquid helium, to the investigation of phonons in crystals. This approach makes possible the study of the propagation and scat tering of phonons of known polarization and propagation direction. The early heat-pulse experiments used phonon generators which pro duced phonons having a broad distribution of energies and, in addi tion, the phonon detectors were sensitive to phonons of all energies.

Download or read book Thermal Energy written by Yatish T. Shah and published by CRC Press. This book was released on 2018-01-12 with total page 854 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book details sources of thermal energy, methods of capture, and applications. It describes the basics of thermal energy, including measuring thermal energy, laws of thermodynamics that govern its use and transformation, modes of thermal energy, conventional processes, devices and materials, and the methods by which it is transferred. It covers 8 sources of thermal energy: combustion, fusion (solar) fission (nuclear), geothermal, microwave, plasma, waste heat, and thermal energy storage. In each case, the methods of production and capture and its uses are described in detail. It also discusses novel processes and devices used to improve transfer and transformation processes.

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

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 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 94 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.