Phonons in polymorphous PbTe films. I. Infrared reflectivity of PbTe films on KCl substrates

Abstract

PbTe films with various thicknesses, grown by laser-assisted deposition on KCl substrates, have been investigated. X-ray diffractograms have been taken in the angular range from 10 degrees to 70 degrees . FIR reflection spectra have been studied in the range from 20 to 5000 cm-1. X-ray diffractograms indicated strained layers with HP PbTe phases: GeS and CsCl type. The frequencies of the infrared modes in these HP phases were determined by fitting the experimental spectra with the reflectance calculated for four media: air and two absorbing layers on absorbing substrate. It was found that the lineshape of the reflectance spectra was governed by a resonant-like frequency dependence of the electron damping parameter. The resonant-like shape of the damping parameter spectrum was attributed to electron scattering off potential wells, formed by dislocations.