The effect of number of carbon atoms in a molecular precursor on the crystallite size in diamond films prepared by plasma-enhanced chemical-vapor deposition

The effect of the number of carbon atoms in a carbon-bearing precursor molecule on the crystallite size in diamond films grown on silicon substrates by microwave plasma-enhanced chemical-vapor deposition is investigated. It is shown that the crystallite size decreases with increasing number of carbon atoms in the molecule. The observed trend correlates with the growth of the C2 line intensity (516.5 nm) in the plasma optical-emission spectrum, which is probably due to participation of C2 radicals in the formation of additional nucleation centers on the surface of a growing diamond film.