Formation of (110) Oriented LiNbO₃ Thin Films on Polycrystalline Diamond Substrates at Low Substrate Temperature

Abstract

Lithium niobate (LiNbO₃) has a piezoelectric property, which make its ideal materials for fabrication of surface acoustic wave (SAW) devices. When the highly oriented LiNbO₃ films are deposited on diamond, a LiNbO₃/diamond layered structure is capable of a wide-bandwidth application in SAW devices at high frequencies. The LiNbO₃ thin films were deposited on diamond-coated silicon substrates by RF reactive sputtering method. When a stoichiometric LiNbO₃ target was used for sputtering target and the cooling efficiency of the target was bad, only LiNb₃O₈ reflections were appeared in X-ray diffraction patterns. It has been suggested that the appearance of the Li-deficient phase of LiNb₃O₈ is caused by the dissociation of the lithium and oxygen from LiNbO₃ during deposition. When an Li enriched LiNbO₃ target was used for sputtering target and the cooling efficiency of the target was good, stoichiometric LiNbO₃ films were prepared and the preferential orientation was (110).