STUDY OF CRYSTALLIZATION OF LINBO3 FILMS FROM METAL ALKOXIDES

The crystallization process of epitaxial LiNbO3 films on sapphire (0001) substrates was investigated by Raman microprobe spectroscopy. LiNbO3 gel films were prepared by the sol-gel method using metal alkoxide precursors on sapphire (0001) substrates and heat treated at various temperatures below 500-degrees-C to produce epitaxial LiNbO3 films. Analyses by electron spectroscopy for chemical analysis and SEM revealed LiNbO3 films were stoichiometric and homogeneous, Raman spectra of the film prepared at 250-degrees-C indicated that the NbO6 octahedral coordination structure in LiNbO3 began to form as the initial state of crystallization. As the heat-treatment temperature was raised, the Raman bands became sharper and increased in spectral intensity and were seen to be the characteristic Raman bands of crystalline LiNbO3. Refractive indices of the obtained films indicated appropriate values. As a method to crystallize the more highly preferred orientation to (006) LiNbO3 film at relatively low temperature, the formation of an underlayer film from diluted solution prior to multiple dip-coating, was found to be very promising.