Improvement of diamond nuclei orientation by double-step bias treatment in microwave plasma-assisted chemical vapor deposition using C2H4 and CH4 as carbon source

Abstract

The effects of bias treatment conditions and carbon sources on the formation of diamond film oriented to an Si(100) substrate were investigated in detail by using microwave plasma-assisted chemical vapor deposition (MPCVD). In the β -SiC formation stage using C 2 H 4 as the carbon source, the most definite mesh structure was formed by a bias treatment at −130 V for 3 min. The mesh structure became ambiguous at smaller bias voltages and was not observed at −50 V. In the subsequent diamond formation step, the optimum bias voltage was −40 V for C 2 H 4 . Faceted diamond particles 5–50 nm in size were formed after 7 min at a population density of (0.8–3) × 10 10 cm −2 , and the fraction of oriented particles was 60%. The population density did not vary with the species of carbon source, but the fraction of oriented particles was larger with C 2 H 4 than with CH 4 under optimized reaction conditions.