Nucleation Studies of Pulsed Bias Enhanced CVD of Diamond on Biomaterials

The effects of bias voltage, bias time, frequency, and duty cycle on the nucleation of diamond were investigated. Pulsed duty cycles were 0.4 mu s, and the frequency varied between 0 and 100 kHz. The substrates were pretreated by a direct current (dc) bias using 3 vol.{\%} CH4 in Ar/H-2 plasma. Growth and surface roughness were controlled using pulsed frequencies, with mean R. values of 20 nm. Films were characterized in terms of orientation and surface roughness using transmission electron microscopy and atomic force microscopy. Bias-enhanced nucleation is shown to profoundly increase the nucleation densities by promoting ion bombardment of the substrate surface, thus creating nucleation sites for subsequent growth on substrates such as titanium alloys and steel. This technology promotes smooth diamond facets without abrasive surface damage. Controlling the surface roughness and morphology is of critical importance for many new biomedical and electronic devices.