Deposition of thick and thin nanocrystalline diamond films by microwave plasma enhanced chemical vapor deposition

Thick (around 3 μm) and thin (48-310 nm) nanocrystalline diamond (NCD) films have been produced from Ar-rich CH4/Ar/H2 (1/89/10 %) and H2-rich CH4/H2 (1/99 %) microwave plasmas, respectively. The thick NCD films were obtained with and without an initial buffer layer (BL). The BL is easily obtained under typical microcrystalline diamond growth conditions (CH4/H2 mixtures). The effect of the deposition temperature (TD, 630-900°C) was investigated on the morphology, the surface roughness and the bonding characteristics of the films grown with and without BL. The thin NCD films were grown on Si substrates treated by two different methods, i.e. ultrasonic agitation in a suspension of diamond powders of 40-60 μm or combinatorial approach in a suspension of mixed diamond powders of 250 nm and 40-60 μm. The present experimental results show that the buffer layer procedure allows a good preservation of the surface of treated Si substrate and the combinatorial approach promotes effectively the seeding of the Si surface.