Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 50 for “"Phonon transport"”.
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Quasiparticle and Phonon Transport in Superconducting Particle Detectors
… SIS and SIN tunnel junctions to investigate the transport of quasiparticles and phonons in structures similar to the proposed detector designs. I have used multiple distributed junction geometries to perform injection-detection type experiments. One junction is used to inject quasiparticles …
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Computational Modeling of Geometry Dependent Phonon Transport in Silicon Nanostructures
… depend on nanostructure boundary geometry. Phonons are quantized mechanical vibrations that are the dominant carrier of heat in semiconductor materials and their aggregate behavior determine a nanostructure's thermal performance. Phonon-geometry scattering processes as well as waveguiding …
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Monte Carlo study of charge and phonon transport in graphene
L argomento principale di questa tesi è lo studio dei fenomeni di trasporto nel grafene. Il graphene è uno dei nuovi materiali più importanti e gode di un ampio spettro di ottime proprietà, che sono raramente presenti assieme in uno stesso materiale, ed è considerato il candidato ideale per lo …
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Dynamical tuning of phonon transport for information and energy control
Controlled transport of energy and information is of paramount importance. It remains challenging, however, partially from the difficulty in controlling their physical carriers. Steering electrons and photons is now routine, yet atomic vibrations (quantized as phonons) are hard to control. This is …
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Nanostructures and alloys : multiple scattering and nonlinearities in phonon transport
Understanding how thermal transport is affected by disorder is crucial to the prediction and engineering of novel materials suitable for thermoelectric and device applications. Ab initio methods have demonstrated accurate calculations of the lattice contribution to thermal conductivity in …
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Low variance methods for Monte Carlo simulation of phonon transport
Computational studies in kinetic transport are of great use in micro and nanotechnologies. In this work, we focus on Monte Carlo methods for phonon transport, intended for studies in microscale heat transfer. After reviewing the theory of phonons, we use scientific literature to write a Monte Carlo …
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Exploring electron and phonon transport at the nanoscale for thermoelectric energy conversion
… these advances, much remains unknown about heat transport in these materials, and further efficiency improvements will require a detailed understanding of how the heat carriers, electrons and phonons, are affected by nanostructures. To elucidate these processes, in this thesis we investigate …
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The effect of surface roughness on thermal and acoustic phonon transport in nanowires and nanomembranes
Phonons are the primary carriers of heat in dielectric solids. In the limit of long wavelength, phonons are essentially sound waves in the solid. The interaction of phonons with crystal surfaces is of fundamental interest in thermal transport as well as in acoustics. This thesis focuses on …
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Effect of phonon transport on the Seebeck coefficient and thermal conductivity of silicon nanowire arrays
… experiments, complemented by charge and thermal transport theories. Electrolessly etched silicon nanowires show anomalously low thermal conductivity that has been attributed to the increased scattering of heat conducting phonons from the surface disorder introduced by etching. The reduction is …
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Theory of electron and phonon transport in nano and molecular quantum devices : design strategies for molecular electronics and thermoelectricity
Understanding the electronic and phononic transport properties of junctions consisting of a scattering region such as a nanoscale region or molecule connected two or more electrodes is the central basis for future nano and molecular scale applications. The theoretical and mathematical techniques to …
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A deviational Monte Carlo formulation of ab initio phonon transport and its application to the study of kinetic effects in graphene ribbons
… method for solving the Boltzmann equation for phonon transport subject to the linearized ab initio 3-phonon scattering operator. Phonon dispersion relations and transition rates are obtained from density functional theory calculations. The ab initio scattering operator replaces the commonly …
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Exploring heat transfer at the atomistic level for thermal energy conversion and management
… introduce atomistic techniques to investigate phonon transport in bulk crystals. We start with normal mode analysis within the classical molecular dynamics framework to estimate the spectral phonon transport properties. Although it can provide the detailed phonon properties adequately, …
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Transport of phonons and electrons in thermoelectric materials and graphene
Understanding transport of phonons and electrons plays a critical role in developing energy conversion and information devices. Thermoelectric materials, which directly convert heat to electricity or vice versa, require both extremely low thermal conductivity and high thermoelectric power factor. …
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Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon
… been some lingering questions surrounding the phonon mean free path and importance of different polarizations. This research investigates phonon transport in bulk crystalline silicon using molecular dynamics and lattice dynamics. The interactions are modeled with the environment dependent …
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Observation and manipulation of the wave nature of phonon thermal transport through superlattices
… 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 …
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Acoustic waves in crystals: I. Ultrasonic flux imaging and internal diffraction. II. Imaging phonons in superconducting niobium
… to such experiments. (I) The low-temperature phonon-imaging technique is extended to ultrasonic frequencies at room temperatures where it is used to study the anisotropic propagation of acoustic waves in crystals. (II) The low-temperature heat-pulse technique is applied to a study of phonon …
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Phonon and electron transport through interfaces and disordered structures
Understanding phonon and electron transport is of great significance for designing efficient solid-state devices such as transistors, laser diodes and thermoelectric energy converters. The structural randomness is inevitable in solid-state devices, and it is often regarded as the undesirable …
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Computational Methods for Studying Phonon Dynamics
… of the structure’s normal modes, often termed phonons, which are collective motions of atoms vibrating at certain frequencies. These vibrational modes play important roles in a variety of material properties and physical phenomena such as chemical reactions, phase transitions, mass/ion …
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Analysis and development of particle based heat transport models for use in nanoscale structures.
… tansport must be used. On the microscale, heat transport can be described by the Boltzmann transport equation for phonons. The complexity and quantity of the phonon anharmonic interactions make a direct numerical solution difficult without numerous approximations. The Monte Carlo technique has …
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