An Approximate Theory of Skin-Effect Acoustic Generation in Conductors

Abstract

Abeles has shown that a marked acoustoelectric coupling can occur due to the penetration of a high‐frequency electric field into a conductor. Calculations are presented here of the coupling due to the spatial phase shift between the Coulomb force on the lattice ions and the reaction force of the electrons, and due to the localized electron reaction on the surface. The latter is largest for diffuse electron reflection, and is the most important coupling mechanism at frequencies above 30 GHz. Efficiencies are fairly low, being in the 10⁻² to 10⁻³ range under ideal conditions; however, they remain of this magnitude up to the lattice vibration frequency. The model used is approximate: a classical free‐electron model, idealized cases of fixed electron free paths with either uniaxial or isotropic electron motion being considered. For specular surface reflection of electrons, the exact model of Quinn is available for comparison, and it is shown that the results are very similar. Single and multilayered film structures are considered in addition to the semi‐infinite conductor.