A method is disclosed for forming a passivating/buffer film on a substrate. The method includes heating the substrate to a temperature which is sufficient to cause a volatilized organometallic precursor to pyrolyze and thereby form a passivating/buffer film on a substrate. The organometallic precursor is volatilized at a precursor source. A carrier gas is directed from a carrier gas source across the precursor source to conduct the volatilized precursor from the precursor source to the substrate. The volatilized precursor pyrolyzes and is deposited onto the substrate, thereby forming the passivating/buffer film on the substrate. The passivating/buffer film can be a cubic-phase passivating/buffer film. An oxide layer can also be formed on the passivating/buffer film to thereby form a composite of the substrate, the passivating/buffer film and the oxide layer. Cubic-phase passivating/buffer films formed by the method of the invention can be lattice-matched with the substrate. Electronic or electro-optical circuits or circuit elements can be formed which include passivating/buffer films formed by the method of the invention.