A versatile metal-halide vapor chemistry for the epitaxial growth of metallic, insulating and semiconducting films

A metal-chloride-based chemistry that bypasses many traditional pitfalls present in the epitaxy of refractory-metal-containing films is described. Methods of dealing with the corrosive chloride-based chemistry in a Molecular Beam Epitaxy (MBE) chamber are detailed. The present state of refractory metal oxide thin film heteroepitaxy is presented along with an explanation of the deposition chemistry involved. To demonstrate the chemical diversity of this technology, oxidation-limited conditions in a vacuum environment are used to grow single crystal epitaxial films of; lithium niobate (LiNbO3), a wide bandgap ferroelectric; lithium niobite (LiNbO2), a semiconducting lithium-metal-oxide; and epitaxial metals niobium and iron. Additionally, the chemistry can easily be applied to other chemical vapor deposition and atomic layer epitaxial growth methods. The novel LiNbO2 thin films are confirmed to have a 2.0 eV bandgap, and several are found to have unusually high p-type conductivities of up to 2500 S/cm.