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Wolfe, J.P. Hurley, Donna Carol 2011-05-16T20:30:46Z 2011-05-16T20:30:46Z 10000-01-01 1988 "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." Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-05-16T20:30:46Z No. of bitstreams: 1 1988_hurley.pdf: 7571100 bytes, checksum: 8c4ebb5868d1c3f31c89986138bc9785 (MD5) Made available in DSpace on 2011-05-16T20:30:46Z (GMT). No. of bitstreams: 1 1988_hurley.pdf: 7571100 bytes, checksum: 8c4ebb5868d1c3f31c89986138bc9785 (MD5) Previous issue date: 1988 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-05-16T20:30:46Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:13:44-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 1856915 http://hdl.handle.net/2142/23896 en 1988 Donna Carol Hurley phonon transmission solid-solid interfaces superlattices phonon imaging low-temperature propagation of heat pulses phonon focusing in cubic crystals heat-pulse propagation Study of phonon transmission through solid-solid interfaces and superlattices by phonon imaging Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.