an improved process for depositing an oxide layer on a substrate by exposing the substrate to a selected vapor phase reactant and an oxygen - containing precursor comprising nitrous oxide mixed with molecular oxygen in a predetermined ratio , in the presence of radiation of a selected wavelength . the radiation causes the direct dissociation of the oxygen - containing precursor to form neutral oxygen atoms that react with the vapor phase reactant and form the oxide , which deposits as a layer on the substrate . the rate of reaction to form and deposit the oxide layer is enhanced by the mixing of molecular oxygen with nitrous oxide in the precursor .