Control of crystallinity in sol-gel derived epitaxial LiNbO3 thin films on sapphire

Control of crystallinity in solid phase epitaxial growth of LiNbO3 thin films derived from methoxyethoxide solution on sapphire substrates has been attempted by investigating growth variables. Crystallization at 700 degrees C for longer than 30min was necessary for full crystallization of LiNbO3 thin films, although the orientations of the LiNbO3 crystal planes parallel to the substrates were almost independent of crystallization temperature and crystallization time. Layer-by-layer crystallization and preparation of an ultrathin initial layer have been found to be important in the growth of high-quality epitaxial LiNBO3 thin alms. X-ray diffraction analysis revealed that perfectly single-plane-oriented epitaxial LiNbO3 thin films, with rocking curve full width at half-maximum of less than 0.07 degrees, were produced on sapphire (001) substrates. Refractive index of 2.24 and optical propagation loss of 3.0dB/cm were achieved.