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 C$_2$ line intensity (516.5 nm) in the plasma optical-emission spectrum, which is probably due to participation of C$_2$ radicals in the formation of additional nucleation centers on the surface of a growing diamond film.