The effects of oxygen and copper impurities on the structure of amorphous germanium

Abstract

We investigated the structural changes which occur with the incorporation of oxygen into amorphous thin films of germanium. The oxygen content of the films was from 1 at.% to a maximum of 10 at.%. The scattered electron intensity for films containing 10 at.% O is similar to that for pure films, but the first amorphous halo is shifted from |s| = 1.923Å−1 to |s| = 1.88Å−1, where |s| = 4π sin θ/λ and s is the momentum transfer vector. For lower oxygen concentrations this shift of the first amorphous halo is proportional to the oxygen content of the films. The radial distribution function of the oxygen-containing films has additional correlation peaks at 1.74, 2.98 and 4.83 Å which are not observed for pure films. From these results we conclude that the effect of the oxygen is to form regions in the random network structure with interatomic distances which resemble those in the tetragonal phase of GeO2 (with some distortions), with the films remaining single-phase, homogenous and amorphous. Films which contain both 10.5 at.% O and 3.4 at.% Cu are shown to be phase separated and to contain widely spaced microcrystal up to 100 Å in diameter. © 1980, All rights reserved.