Preparation and structural analysis of SnTe/Sb composition modulated structures

Abstract

A new composition modulated structure composed of semiconducting SnTe and semimetallic Sb has been grown epitaxially on mica substrates with differing SnTe to Sb ratios. The samples were characterized by x-ray diffraction using the transmission Laue patterns and θ-2θ diffractometer scans with scattering vectors both normal and in the plane of the film. We observed that the modulation satellites were 180° out of phase for films with short modulation wavelengths, but were in phase for long wavelengths. This change in the phase of the modulation can be understood by assuming that Sb adopts a quasicubic structure at short modulation wavelength, due to the coherency strain, but relaxes back to a distorted rhombohedral structure, with the loss of coherency, at long wavelengths. A simple 1-D model was used to estimate the modulation wavelength dependence of the sublattice displacement of Sb.