Effects of ion bombardment on the nucleation and growth of diamond films

The influence of ion bombardment on the nucleation and growth of diamond films by microwave plasma chemical vapor deposition (CVD) has been investigated The following findings were obtained. (i) Modification of surface diffusion by a substrate bias voltage was demonstrated by the measurement of the first-nearest-neighbor distances. The satisfactory agreement of the nucleation rate with a kinetic model describing the formation of active sites, germs, and nuclei was computer-simulated using crystal-size-distribution data under consideration of a linear growth mechanism. (ii) A dependence of growth direction of diamond grains upon the orientation of ion bombardment was observed using an atomic force microscopic analysis. (iii) Using a combination of scanning electron microscopy and transmission electron microscopy, slight misorientations of crystallites, homoepitaxially grown on (001) diamond faces parallel to the substrate, were found and analyzed. The findings confirm the role of ion impact in diamond CVD and help to understand the basic mechanism responsible for the crystal orientation in heteroepitaxial diamond films prepared using bias-enhanced nucleation. A detailed study of H+ ion etching selectivity was performed in order to obtain insight into the basic mechanism of the observed effects.