Abstract
In a crystal with a free surface the translational symmetry in one direction is raised. In this case it is possible to reduce the equation of motion of the crystal to a form which is analogous to the equation of motion of a semi-infinite generalized linear chain. In this picture the surface-phonons correspond to boundary vibrations of the chain. Methods to calculate the frequencies and the “damping” constant of the surface-phonons are shown. If the surface exhibits a symmetric structure it is possible to classify the frequencies according to the irreducible representations of a subgroup of the surface-space-group.
Model-calculations are performed for a free Si-111-surface using a six-parameter potential (fitted to dispersion curves). The change of the force constants near the surface is considered and fitted to the experiment of Ibach (ν=13.3×1012 sec−1). With the obtained weakening of the potential near the surface, dispersion-curves for surface-phonons are calculated.
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Extract from dissertation (D 26), Gießen 1973.
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Zimmermann, R. Surface-phonons at a free-111-surface of Si. Appl. Phys. 3, 235–239 (1974). https://doi.org/10.1007/BF00884503
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DOI: https://doi.org/10.1007/BF00884503