Fabrication and x-ray photoelectron spectroscopy of granular Ge in Al and Al2O3 matrices

Granular Ge films consisting of Ge grains uniformly dispersed in Al and Al2O3 matrices were prepared by magnetron sputtering. Films were deposited by either cosputtering a Ge target and an appropriate matrix target or, as in the case of Al2O3, by sputtering composite targets pressed from mixtures of Ge and Al2O3 powders. Films containing 10%–90% Ge were fabricated in both the cases. Transmission electron microscopy analyses of the Ge–Al films indicate a granular to nongranular microstructure transition with composition. In the Ge–Al2O3 system similar granular microstructure is obtained at low Ge concentrations; but high Ge concentration films, although phase separated, did not have microstructure typical of the granular films. The granular films have grain size ranging between 20 and 100 nm. X‐ray photoelectron spectroscopy analyses of Ge–Al films indicate the presence of small amounts of oxygen in the films, perhaps from the residual gases in the system or from the targets. This oxygen, however, was foun...