Deposition of c-BN films on diamond: influence of the diamond roughness

Diamond films deposited on Si substrates by Plasma Enhanced Chemical Vapor Deposition (PECVD) were used as substrates for c-BN thin film deposition. T he c-BN films were deposited at 400 degrees C by Ion Beam Assisted Depositi on (IBAD) using a mixture of nitrogen and argon ions. In term of roughness, two kinds of diamond films were chosen, i.e. naturally rough diamond with roughness values ranging from 100 to 200 nm (r.m.s) and planarized diamond films with a roughness value of 16 nm (r.m.s). From IR analyses, it was sho wn that the fraction of cubic phase in the c-BN films was depending on the roughness of the diamond surface. As expected, this fraction in cubic phase was optimized in the case of smooth surfaces presenting no particular geom etrical effect for the incoming energetic nitrogen and argon ions. These re sults clearly showed the necessity to have planarized and smooth diamond su rfaces prior to the c-BN film deposition. TEM study perfomed on c-BN films deposited on planarized diamond revealed that the films were nanocrystallin e with columnar grains. A HRTEM study focused on the interface between the c-BN film and the substrate showed the commonly observed layered structure, i.e. a well textured c-BN volume lying on a h-BN basal layer with the (00. 2) planes perpendicular to the substrate. (C) 1999 Elsevier Science S.A. Al l rights reserved.