Selection rules of Raman scattering by optical phonons in strained cubic crystals
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Anastassakis, E
(EN)
Strain characterization of materials through Raman spectroscopy often requires the optical phonon wave vector to be in directions other than those of the strain-modified phonon eigenvectors. As a result, the observed mode frequencies are mixtures of the strain-modified eigenfrequencies. The selection rules for such generalized scattering configurations are derived here for the strained zincblende-diamond family crystals. The formulation is based on the relative magnitude of the LO-TO and the strain-induced splittings. The results are important for the analysis of strain-modified Raman lineshapes and of ''forbidden'' lines. Specific examples;are worked out in derail for externally stressed bulk crystals (90 degrees scattering geometry), and for [001], [111], and [110] strained heterojunctions (backscattering under oblique incidence and/or detection). (C) 1997 American Institute of Physics.
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