An X-ray diffraction study of epitaxial lithium tantalate films deposited on (0001) sapphire wafers using r.f. diode sputtering

Abstract

Epitaxial thin films of lithium tantalate have been r.f. diode sputtered onto (0001) single-crystal sapphire substrates. X-ray diffraction results show that, as the Li/(Li + Ta) ratio decreased below 0.5, the LiTaO 3 (LTO type) c-axis lattice constant increased. An additional lithium tantalate phase is observed to coexist with the LTO-type phase at a Li/(Li + Ta) ratio of around 0.4. When the Li/(Li + Ta) ratio becomes close to 0.25, this additional phase is the only phase observed in the sputter-deposited thin film. Tilt-angle X-ray diffraction results confirmed that this additional phase is ilmenite-type (IL type) Li( 1 − x) TaO 3.