Frequency-Dependence of Pulsed Bias-Enhanced Nucleation of Diamond on (100) Silicon

Bias-enhanced nucleation (BEN) is a technique whereby energetic substrate bombardment of ionized species has a profound effect on the promotion of diamond nucleation. Ion sub-plantation and enhanced surface mobilities of carbonaceous species have been proposed to explain the high nucleation densities as well as epitaxial diamond formed on pristine silicon and SiC. We have studied pulsed BEN to improve upon earlier results of dc-BEN on epitaxial diamond formation and to better understand the dynamics of the plasma sheath region and its effects on bias-enhanced nucleated diamond. Pulsed BEN was performed on (100) silicon substrates using a 17% duty cycle and varying bias frequency in the range of 1 Hz to 2 kHz. We observed a constant proportion of highly oriented diamond of 50% as a function of this relatively low bias frequency range; the transit time of ions through the plasma sheath would be subject to essentially freezing-out only at frequencies on the order of megahertz. A linear increase in bias current with bias frequency, and correspondingly, a linear decrease in the bias duration required to form a quasi-continuous film of diamond was observed.