Local laser-assisted chemical vapor deposition of diamond

Diamond spots are grown in a hot filament CVD reactor from CH4/H-2 gas mixt ure on a supported thin tungsten him. Local growth is achieved by confined heating of the substrate using the focused beam of a cw Nd-YAG laser. Thus, diamond spots with a size of similar to 30 mum were obtained. The spots ar e characterized by scanning electron microscopy and micro Raman spectroscop y. The growth rate and the spot structure strongly depends on the nucleatio n density which could be controlled by ultrasonic treatment of the sample i n a diamond powder-ethanol mixture prior to deposition. At low nucleation d ensity the spot consists of separate crystallites with the size decreasing with the distance from the center in accordance with an inhomogeneous laser -induced temperature distribution. At high nucleation density a flat microc rystalline diamond disk is grown with a uniform grain size due to a flat to p temperature profile. Already at the early stages of the deposition, therm al contact has been achieved between the crystallites, homogeneous temperat ure distribution forms due to the high thermal conductivity of the diamond film. (C) 2000 Elsevier Science B.V. All rights reserved.