Effect of substrates on the crystallinity and morphology of sol-gel-derived epitaxial LiNbO3 films

Abstract

Epitaxial thin films of LiNbO3 were prepared by the sol-gel method on (0001)-sapphire, (0001)-LiTaO3 and (0001)-5% MgO-doped LiNbO3, substrates. The precursor films crystallized with the highly preferred orientation on all substrates. When sapphire substrates, which have large discrepancies in the lattice constant and thermal expansion percentage with the film were used, the resulting films showed a low crystallinity after heat treatment at 500 °C and grain growth at 650 °C. On the other hand, when using LiTaO3 and 5% MgO-doped LiNbO3 substrates, with smaller discrepancies, the formed films, after heat treatment at 500 °C, showed better crystallinity with the smooth surface.