Microstructural Variations in Sol-Gel Processed Lithium Niobate thin Films

LiNbO 3 thin films were deposited by dip coating Li-Nb alkoxide solutions onto silicate glass substrates and single crystal sapphire substrates. Microstructural characterization using transmission electron microscopy (TEM) showed significant differences in film microstructures dependent on the initial solution chemistry. Fully crystalline films could be obtained after heat treatments at 400°C in air. The grain size and porosity were dependent on the amount of water of hydrolysis in the alkoxide sol. The higher the water content, the larger the grain size and porosity. Crystallization studies of nucleation and growth of LiNbO 3 for films heat treated from 300–600°C indicated that higher temperatures or long soak times generated large facetted grain structures. Single crystalline films were obtained on (0001) sapphire substrates.