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Title:Study of phonon transmission through solid-solid interfaces and superlattices by phonon imaging
Author(s):Hurley, Donna Carol
Doctoral Committee Chair(s):Wolfe, J.P.
Department / Program:Physics
Subject(s):phonon transmission
solid-solid interfaces
phonon imaging
low-temperature propagation of heat pulses
phonon focusing in cubic crystals
heat-pulse propagation
Abstract:The work in this thesis explores the low-temperature propagation of heat pulses (phonons) through crystals and across solid-solid interfaces. The phonon imaging technique has been used to examine the angular and temporal dependence of the phonon-flux intensity in several systems, listed below. 1. Phonon focusing in cubic crystals. The nature of the intensity pattern associated with phonon propagation is examined theoretically for cubic crystals in general. Experimental images, Monte Carlo fluxintensity simulations, and the slowness-surface topology are analyzed in detail for a wide range of elastic constants. A classification is developed whereby the pattern of phonon-focusing caustics may be predicted for any cubic material given its elastic constants and density. 2. Heat-pulse propagation across a copper-diamond interface. Phonon imaging experiments in diamond reveal sharp structures in addition to phonon-focusing caustics. The structures correspond to the channeling of transverse phonons close to the critical cone for mode conversion of transverse to longitudinal waves at the diamond surface. The process is mediated by pseudo-surface waves, and provides information about the quality of the diamond surface and the mechanical bonding of the copper/diamond interface. 3. Phonon transmission through superlattices. Phonon imaging experiments on several InxGa"xAs/A1As and A1As/GaAs superlattices examine the angular distribution of high-frequency acoustic phonon transmission through periodic superlattices. Bragg reflection of phonons is studied in detail, and related to gaps, or stopbands, in the phonon dispersion relation. Attenuation in the phonon transmission due to gaps at the folded Brillouin zone boundary are observed for both longitudinal and fast transverse phonons. A newly predicted stopband within the zone due to coupling between the transverse and longitudinal acoustic modes is detected. The experimental results are compared to calculations of the transmission rate and the angular stopband distribution.
Issue Date:1988
Genre:Dissertation / Thesis
Rights Information:1988 Donna Carol Hurley
Date Available in IDEALS:2011-05-16
Identifier in Online Catalog:1856915

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