Diamond growth during bias pre-treatment in the microwave CVD of diamond

We have investigated the spatiotemporal development of the plasma during the bias pre-treatment that precedes the chemical vapour deposition (CVD) of diamond and the chemical composition, the identity of carbon modifications, and the topography of the substrate surfaces after selected stages of the biasing. The methods employed were X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy as well as scanning electron microscopy (SEM). Areas of high diamond nucleation density were identified at each stage by interrupting the bias pre-treatment, switching to growth conditions and screening for diamond crystals after growth for Ih with SEM. After about 10 min the biasing alone yields an almost pure diamond surface as judged by the loss features in XPS although neither Raman spectroscopy nor SEM give any indication thereof. In particular, for the growth of highly oriented textured diamond films, the stage at which the biasing is stopped is crucial since prolonged growth of diamond under biasing conditions destroys the initial orientation of the diamond nuclei.