Epitaxial growth and characterization of stoichiometric LiNbO3 films prepared by the sol-gel method

After stoichiometric LiNbO3 thick films were deposited on z-cut LiNbO3 substrates using the sol-gel method from a precursor solution containing various polyvinyl alcohol (PVA) concentrations, their characteristics were investigated. The film thickness increased linearly with the increase in PVA and precursor concentrations. The orientation relationships between films and substrates were determined by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, and the results showed that (006) oriented LiNbO3 epitaxial layers with parallel epitaxial relationships could be grown on a z-cut LiNbO3 substrate. The refractive indexes of the films were n0=2.28±0.02 and ne=2.19±0.02 at a wavelength of 632.8nm, and their transmission loss was 0.50±0.04dB∕cm.