Local laser-assisted chemical vapor deposition of diamond

Abstract Diamond spots are grown in a hot filament CVD reactor from CH4/H2 gas mixture on a supported thin tungsten film. 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 ∼30 μm were obtained. The spots are characterized by scanning electron microscopy and micro Raman spectroscopy. The growth rate and the spot structure strongly depends on the nucleation density which could be controlled by ultrasonic treatment of the sample in a diamond powder–ethanol mixture prior to deposition. At low nucleation density 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 microcrystalline diamond disk is grown with a uniform grain size due to a flat top temperature profile. Already at the early stages of the deposition, thermal contact has been achieved between the crystallites, homogeneous temperature distribution forms due to the high thermal conductivity of the diamond film.