Abstract: A composite comprising a monocrystalline substrate and one or more layers or films of monocrystalline IVA-VIA compounds and/or alloys formed thereon by a chemical vapor deposition process. The composite is formed at a preferred temperature range of approximately 450.degree.-650.degree. C. The IVA-VIA layer(s) are produced by the pyrolysis of a gas mixture containing metalorganic compounds. Where single crystal metallic oxide substrates of rhombohedral structure, such as sapphire, (.alpha.-Al.sub.2 O.sub.3), or of cubic structure, such as magnesium aluminate (spinel), are used for the growth of monocrystalline lead-containing films such as Pb.sub.1-x Sn.sub.x Te, a nucleation layer of lead is preferably formed on the substrate prior to the pyrolysis of the mixed gaseous reactants.