AN X-RAY-DIFFRACTION STUDY OF EPITAXIAL LITHIUM TANTALATE FILMS DEPOSITED ON (0001)SAPPHIRE WAFERS USING RF DIODE SPUTTERING

Epitaxial thin films of lithium tantalate have been r.f. diode sputter ed onto (0001) single-crystal sapphire substrates. X-ray diffraction r esults show that, as the Li/(Li+Ta) ratio decreased below 0.5, the LiT aO3 (LTO type) c-axis lattice constant increased. An additional lithiu m 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 clos e to 0.25, this additional phase is the only phase observed in the spu tter-deposited thin film. Tilt-angle X-ray diffraction results confirm ed that this additional phase is ilmenite-type (IL type) Li-(1-x)TaO3.