Ion beam sputter deposition of Ge films: Influence of process parameters on film properties

Several sets of Ge films were grown by ion beam sputter deposition under systematic variation of ion beam parameters (ion species and ion energy) and geometrical parameters (ion incidence angle and polar emission angle). The films were characterized concerning thickness, growth rate, mass density, structural properties and composition. The film thicknesses show a cosine-like angular distribution, and the growth rates were found to increase with increasing ion incidence angle and ion energy. All films are amorphous and the average mass density was found to be (4.3±0.2) g/cm3, without a systematic relation to ion energy and geometrical parameters. Slightly higher mass densities were found for Ge films grown by sputtering with Xe than for sputtering with Ar. The Ge films contain a fraction of inert gas atoms from backscattered primary particles. This fraction is found to be higher for sputtering with Ar than for sputtering with Xe. The fraction of inert gas atoms increases with increasing polar emission angle and increasing ion incidence angle. Raman scattering experiments revealed also systematic shifts of the characteristic Raman mode. The shifts are tentatively assigned to the change of the Ge particle densities caused by the incorporation of inert gas particles. There seem to be also slight changes in short range ordering. The experimental data are discussed with respect to the known energy and angular distributions of the sputtered and backscattered particles.