The epitaxial growth of selenium on ionic substrates

Abstract

Thin films of selenium have been prepared on single crystal substrates by vacuum evaporation of selenium and condensation onto the heated substrate. Reviews are given of the phenomenon of epitaxy, the structure of the allotropes of selenium, and the previous work on selenium films having any "bearing on the problem of epitaxial growth. Techniques are described for the preparation of single crystal substrates, the deposition of selenium films, and their removal from the substrate. Transmission electron micrography and diffraction were used to examine the films. Conditions were established for the epitaxial growth of selenium on (100) and (110) potassium bromide, and the relative orientations of the film and the substrate determined. Films were also prepared on (100), (110), and (111) sodium chloride, (111) potassium bromide, (100) magnesium oxide, and (III) calcium and barium fluoride. These latter films were found to be polycrystalline or amorphous. Film thickness was determined by the measurement of the area and the chemical determination of the mass of the film. The structure and orientation of the films is discussed in terms of misfit of the substrate and overgrowth lattices, and particularly in terms of recent work on crystal surfaces.