A Model for Calculating Pseudosurface Wave Structures in Phonon Imaging
The intensity variation in phonon images derives principally from two sources: phonon focusing in the bulk of the crystal, and the directional emissivity of the surfaces across which the phonons enter and leave the crystal. The role that phonon focusing plays has been explored in numerous publications . Recently surface directivity effects have been reported in highly polished sapphire [2,3] and diamond  single crystals. Pronounced halos of enhanced phonon intensity are observed close to the critical cones for mode conversion of transverse to longitudinal waves at the crystal surface, and these have been interpreted as the signature of pseudosurface waves (PSW’s) in the quasi-free crystal surface. In this paper we describe a simple model for treating the directional dependence of the phonon emissivity and absorptivity of the crystal surface.
KeywordsAnisotropy Sapphire Emissivity Acoustics
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