Download or read book Measuring Phonon Mean Free Path Distributions by Probing Quasiballistic Phonon Transport in Grating Nanostructures written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domain thermoreflectance measurements and simultaneously act as wiregrid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. Furthermore, this table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials.
Download or read book Transport Phenomena in Micro and Nanoscale Functional Materials and Devices written by Joao B. Sousa and published by William Andrew. This book was released on 2021-03-23 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transport Phenomena in Micro- and Nanoscale Functional Materials and Devices offers a pragmatic view on transport phenomena for micro- and nanoscale materials and devices, both as a research tool and as a means to implant new functions in materials. Chapters emphasize transport properties (TP) as a research tool at the micro/nano level and give an experimental view on underlying techniques. The relevance of TP is highlighted through the interplay between a micro/nanocarrier’s characteristics and media characteristics: long/short-range order and disorder excitations, couplings, and in energy conversions. Later sections contain case studies on the role of transport properties in functional nanomaterials. This includes transport in thin films and nanostructures, from nanogranular films, to graphene and 2D semiconductors and spintronics, and from read heads, MRAMs and sensors, to nano-oscillators and energy conversion, from figures of merit, micro-coolers and micro-heaters, to spincaloritronics. Presents a pragmatic description of electrical transport phenomena in micro- and nanoscale materials and devices from an experimental viewpoint Provides an in-depth overview of the experimental techniques available to measure transport phenomena in micro- and nanoscale materials Features case studies to illustrate how each technique works Highlights emerging areas of interest in micro- and nanomaterial transport phenomena, including spintronics
Download or read book Studying Phonon Mean Free Paths at the Nanoscale written by Lingping Zeng and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat conduction in semiconductors and dielectrics involves cumulative contributions from phonons with different frequencies and mean free paths (MFPs). Knowing the phonon MFP distribution allows us to gain insight into the fundamental microscopic transport physics and has important implications for many energy applications. The key metric that quantifies the relative contributions of different phonon MFPs to thermal conductivity is termed thermal conductivity accumulation function. In this thesis, we advance a thermal conductivity spectroscopy technique based upon experimental observation of non-diffusive thermal transport using wire grid linear polarizer in conjunction with time-domain thermoreflectance (TDTR) pump-and-probe measurement setup. Consistent algorithm based on solution from the phonon Boltzmann transport equation (BTE) is also developed to approximately extract the thermal conductivity accumulation functions in materials studied. The heat flux suppression function appropriate for the experimental sample geometry relates the measured apparent thermal conductivities to the material's phonon MFP distributions. We develop a multi-dimensional thermal transport model based on the gray phonon BTE to find the suppression function relevant to our spectroscopy experiment. The simulation results reveal that the suppression function depends upon both the heater size and the heater array period. We also find that the suppression function depends significantly on the location of the temperature measurement. Residual suppression effect is observed for finite filling fractions (ratio of heater size to heater array period) due to the transport coupling in the underlying substrate induced by the neighboring heaters. Prior phonon MFP spectroscopy techniques suffer from one or several of the following limitations: (1) diffraction limited to micrometer lengthscales by focusing optics, (2) applying only to transparent materials, or (3) involving complex micro-fabrications. We explore an alternate approach here using wire grid linear polarizer in combination with TDTR measurement. The wire grid polarizer is designed with sub-wavelength gaps between neighboring heaters to prevent direct photo-excitation in the substrate while simultaneously functioning as heaters and thermometers during the measurement. The spectroscopy technique is demonstrated in crystalline silicon by studying length-dependent thermal transport across a range of lengthscales and temperatures. We utilize the calculated heat flux suppression functions and the measured size-dependent effective thermal conductivities to reconstruct the phonon MFPs in silicon and achieve reasonably good agreement with calculation results from first principle density function theory. Knowledge of phonon MFP distributions in thermoelectric materials will help design nanostructures to further reduce lattice thermal conductivity to achieve better thermoelectric performance in the next-generation thermoelectric devices. We apply the developed wire grid polarizer spectroscopy technique to study phonon MFP distributions in two thermoelectric materials: Nb0.95 Ti0.05FeSb and boron-doped nanocrystalline Si80Ge20B. We find that the dominant phonon MFPs that contribute to thermal conductivity in those two materials are in the a few tens to a few hundreds of nanometers. The measurement results also shed light on why nanostructuring is an effective approach to scattering phonons and improve the thermoelectric behavior.
Download or read book Polymer Based Multifunctional Nanocomposites and Their Applications written by John Zhanhu Guo and published by Elsevier. This book was released on 2018-09-14 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer-Based Multifunctional Nanocomposites and Their Applications provides an up-to-date review of the latest advances and developments in the field of polymer nanocomposites. It will serve as a one-stop reference resource on important research accomplishments in the area of multifunctional nanocomposites, with a particular emphasis placed on the use of nanofillers and different functionality combinations. Edited and written by an expert team of researchers in the field, the book provides a practical analysis of functional polymers, nanoscience, and nanotechnology in important and developing areas, such as transportation engineering, mechanical systems, aerospace manufacturing, construction materials, and more. The book covers both theory and experimental results regarding the relationships between the effective properties of polymer composites and those of polymer matrices and reinforcements. Presents a thorough and up-to-date review of the latest advances and developments in the field of multifunctional polymer nanocomposites Integrates coverage of fundamentals, research and development, and the range of applications for multifunctional polymers and their composites, such as in the automotive, aerospace, biomedical and electrical industries Supports further technological developments by discussing both theory and real world experimental data from academia and industry
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 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 Experimental and Numerical Investigation of Phonon Mean Free Path Distribution written by Lingping Zeng and published by . This book was released on 2013 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Knowledge of phonon mean free path (MFP) distribution is critically important to engineering size effects. Phenomenological models of phonon relaxation times can give us some sense about the mean free path distribution, but they are not accurate. Further improvement of thermoelectric performance requires the phonon MFP to be known. In this thesis, we improve recently developed thermal conductivity spectroscopy technique to experimentally measure MFPs using ultrafast transient thermoreflectance method. By optically heating lithographically patterned metallic nanodot arrays, we are able to probe heat transfer at length scales down to 100 nm, far below the diffraction limit for visible light. We demonstrate the new implementation by measuring MFPs in sapphire at room temperature. A multidimensional transport model based on the grey phonon Boltzmann equation is developed and solved to study the quasi-ballistic transport occurring in the spectroscopy experiments. To account for the nonlinear dispersion relation, we present a variance reduced Monte Carlo scheme to solve the full Boltzmann transport equation and compare the simulation results with experimental data on silicon.
Download or read book Multifunctional Epoxy Resins written by Nishar Hameed and published by Springer Nature. This book was released on 2023-01-01 with total page 439 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consolidates information about multifunctional epoxy as a frontier material, its composites, engineering and applications in a very detailed manner that encompasses the entire spectrum of up-to-date literature citations, current market trends and patents. It highlights latest experimental and theoretical studies on the atypical properties of epoxy resins such as self-healing, thermally and electrically conductivity; and its applications in devices where there is reliance on unsustainable sourced inorganic materials with comparable properties. It caters to polymer chemists, physicists and engineers who are interested in the field of next generation epoxy polymers.
Download or read book Phonon Focusing and Phonon Transport written by Igor Gaynitdinovich Kuleyev and published by Walter de Gruyter GmbH & Co KG. This book was released on 2020-06-08 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: The monograph is devoted to the investigation of physical processes that govern the phonon transport in bulk and nanoscale single-crystal samples of cubic symmetry. Special emphasis is given to the study of phonon focusing in cubic crystals and its influence on the boundary scattering and lattice thermal conductivity of bulk materials and nanostructures.
Download or read book Optical Transient Grating Measurements of Micro nanoscale Thermal Transport and Mechanical Properties written by Jeffrey Kristian Eliason and published by . This book was released on 2015 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: The laser-based transient grating technique was used to study phonon mediated thermal transport in bulk and nanostructured semiconductors and surface wave propagation in a monolayer of micron sized spheres. In the transient grating technique two picosecond pulses are crossed to generate a spatially periodic intensity profile. The spatially periodic profile generates a material excitation with a well-defined wave vector. The time dependence of the spatially periodic material response is measured by monitoring the diffracted signal of an incident probe beam. Non-diffusive thermal transport was observed in thin Si membranes as well as bulk GaAs at relatively short (micron) transient grating periods. First-principles calculations of the phonon mean free paths in Si and GaAs were compared with experimental results and showed good agreement. Preliminary measurements on promising thermoelectric materials such as PbTe and Bi2Te3 are presented showing evidence of non-diffusive transport at short length scales. The transient grating technique was used to measure the thermal conductivity of Si membranes with thickness ranging from 15 nm to 1518 nm. Using the Fuchs-Sondheimer suppression function along with first-principles results, the thermal conductivity as a function of membrane thickness was calculated. The calculations showed excellent agreement with experimental measurements. A convex optimization algorithm was employed to reconstruct the phonon mean free path distribution from experimental measurements. This marks the first experimental determination of the mean free path distribution for a bulk material. Thermal conductivity measurements at low temperatures in a 200 nm Si membrane indicate the breakdown of the diffuse boundary scattering approximation. The transient grating technique was used to generate surface acoustic waves and measure their dispersion in a monolayer of 0.5 - 1 [mu]m diameter silica spheres. The measured dispersion curves show "avoided crossing" behavior due to the interaction between an axial contact resonance of the microspheres and the surface acoustic wave at a frequency of -200MHz for the 1 [mu]m spheres and -700 MHz for the 0.5 [m spheres. The experimental measurements were fit with an analytical model in which the contact stiffness was the only fitting parameter. Preliminary results of surface acoustic wave propagation in microsphere waveguides, transmission through a microsphere strip, and evidence of a nonlinear response in a 2D array of microspheres are presented.
Download or read book Advances in Understanding Thermal Effects in Rubber written by Gert Heinrich and published by Springer Nature. This book was released on with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Carrier Transport In Nanostructures written by Obafemi Oluwaseun Otelaja and published by . This book was released on 2016 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectrally resolved phonon transport is important for understanding nanoscale heat flow, which have implications for the realization of efficient thermoelectric and microelectronic cooling devices, for the realization of efficient cryogenic particle detectors, and for the realization of robust implementations of quantum computers. This thesis describes the development and utilization of a microscale phonon spectrometer. Aluminum superconducting tunnel junctions (STJ) are utilized for the emission and detection of non-thermal phonons with frequencies ranging from ~100 to ~870 GHz in silicon nanostructures. The energy resolution of the spectrometer is ~6080 [mu]eV, corresponding to a frequency resolution of ~15-20 GHz, which is about 20 times better than the energy resolution of conventional thermal transport measurements that rely on a Planck distribution of phonons. The spectrometer is utilized to probe surface scattering and phonon backscattering in silicon. To probe surface scattering, silicon nanosheets were fabricated, their surface roughness (~1 nm) was determined using atomic-force microscopy, and their phonon scattering rates were measured. Our results indicate that the well-known Ziman theory, which takes into account the roughness of the surface, underestimates the probability for totally diffusive scattering in nanostructures. To probe phonon backscattering, phonon 'enhancers' (~90 [mu]m deep) were etched around the STJ detectors, and the measured backscattered phonon signal increases with the number of enhancers. Using a geometric analysis of the phonon pathways, we show that the mechanism of the backscattered phonon enhancement is due to confinement of the ballistic phonon. These results have implications for ballistic phonon transport, phonon-mediated detection, and thermal transport studies, and highlight the important effects of phonon scattering from surfaces and interfaces in nanoscale geometrical designs. Finally, a facile room-temperature method, comprising ammonium sulfide treatment and electrophoretic deposition, was developed for assembling colloidal copper sulfide (Cu2-xS) nanoparticles into highly electrically conducting films. Electronic properties of the treated films are characterized with a combination of Hall Effect measurements, field-effect transistor measurements, temperature-dependent conductivity measurements, and capacitance-voltage measurements, revealing their highly-doped p-type semiconducting nature. In addition to being important for solutionprocessed electronics, the periodicity introduced by nanoparticles and their arrays presents a model system for probing phonon transport in complex interfaces.
Download or read book Phonon Dynamics and Thermal Transport in Surface disordered Nanostructures written by Leon Nathaniel Maurer and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation examines the effects of surface disorder on phonon dynamics through two different but complementary approaches. First, we use a phonon Monte Carlo (PMC) simulation with random, rough surfaces. PMC is an excellent tool for studying nanostructures of experimentally relevant sizes. We detail our PMC method, including improvements over previous PMC simulations. We investigate why rough silicon nanowires have measured thermal conductivities about two orders of magnitude lower than predicted and comparable to amorphous materials. We show that it can be largely explained through scattering from rough surfaces; extreme roughness causes a qualitative change in how phonons interact with boundaries. During this project, we uncovered the utility of the geometric mean free path (GMFP), which is a concept developed in the study of chaotic billiards. The GMFP is the average distance a particle travels between surface scattering events (in the absence of other scattering mechanisms), and we show that the thermal conductivities obtained from our PMC simulations are a function of the GMFP. Second, we study two-dimensional elastic nanoribbons using finite-difference methods. Elastic materials make good model systems for studying lattice dynamics because elastic materials capture wave behavior, and, in the long-wavelength limit, phonons behave like elastic waves. Our elastic-medium finite-difference time-domain (FDTD) simulation allows us to efficiently model relatively large structures while still treating phonons as waves. We develop a technique to calculate the thermal conductivity of elastic nanoribbons by coupling our FDTD simulation with the Green-Kubo formula. We also employ a time-independent finite-difference (TIFD) method to solve for and study individual modes of our system. We find that rough surfaces can have an outsize impact on phonon dynamics. Surfaces do not simply scatter phonons; rough surfaces can also trap energy and cause all modes throughout the system to localize. The energy trapping and localization coincide with reduced thermal conductivity. We also investigate the effects of Rayleigh waves, a nonbulk mode often ignored in phonon transport simulations. We use TIFD methods to search for signs of wave chaos in nanoribbons. We find an interesting connection between the GMFP and thermal conductivity, which points the way towards future work.
Download or read book Phonon Dynamics and Thermal Transport in Surface disordered Nanostructures written by Leon Nathaniel Maurer and published by . This book was released on 2016 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation examines the effects of surface disorder on phonon dynamics through two different but complementary approaches. First, we use a phonon Monte Carlo (PMC) simulation with random, rough surfaces. PMC is an excellent tool for studying nanostructures of experimentally relevant sizes. We detail our PMC method, including improvements over previous PMC simulations. We investigate why rough silicon nanowires have measured thermal conductivities about two orders of magnitude lower than predicted and comparable to amorphous materials. We show that it can be largely explained through scattering from rough surfaces; extreme roughness causes a qualitative change in how phonons interact with boundaries. During this project, we uncovered the utility of the geometric mean free path (GMFP), which is a concept developed in the study of chaotic billiards. The GMFP is the average distance a particle travels between surface scattering events (in the absence of other scattering mechanisms), and we show that the thermal conductivities obtained from our PMC simulations are a function of the GMFP. Second, we study two-dimensional elastic nanoribbons using finite-difference methods. Elastic materials make good model systems for studying lattice dynamics because elastic materials capture wave behavior, and, in the long-wavelength limit, phonons behave like elastic waves. Our elastic-medium finite-difference time-domain (FDTD) simulation allows us to efficiently model relatively large structures while still treating phonons as waves. We develop a technique to calculate the thermal conductivity of elastic nanoribbons by coupling our FDTD simulation with the Green-Kubo formula. We also employ a time-independent finite-difference (TIFD) method to solve for and study individual modes of our system. We find that rough surfaces can have an outsize impact on phonon dynamics. Surfaces do not simply scatter phonons; rough surfaces can also trap energy and cause all modes throughout the system to localize. The energy trapping and localization coincide with reduced thermal conductivity. We also investigate the effects of Rayleigh waves, a nonbulk mode often ignored in phonon transport simulations. We use TIFD methods to search for signs of wave chaos in nanoribbons. We find an interesting connection between the GMFP and thermal conductivity, which points the way towards future work.
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 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 Nanoscale Energy Transport written by LIAO and published by IOP Publishing Limited. This book was released on 2020-03-20 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together leading names in the field of nanoscale energy transport to provide a comprehensive and insightful review of this developing topic. The text covers new developments in the scientific basis and the practical relevance of nanoscale energy transport, highlighting the emerging effects at the nanoscale that qualitatively differ from those at the macroscopic scale. Throughout the book, microscopic energy carriers are discussed, including photons, electrons and magnons. State-of-the-art computational and experimental nanoscale energy transport methods are reviewed, and a broad range of materials system topics are considered, from interfaces and molecular junctions to nanostructured bulk materials. Nanoscale Energy Transport is a valuable reference for researchers in physics, materials, mechanical and electrical engineering, and it provides an excellent resource for graduate students.
