Processing of highly oriented lithium tantalate films by chemical solution deposition

The synthesis of lithium tantalate films by a chemical solution deposition method was studied. A precursor solution was prepared by dissolving lithium ethoxide and tantalum pentaethoxide in ethanol. The addition of formic acid to this precursor solution was very effective in the preparation of homogeneous and transparent precursor films on substrates by spin coating. Lithium tantalate films crystallized on sapphire (001) substrates with a highly preferred orientation along the c axis with heat-treating at temperatures above 450 °C. The refractive index of the film prepared at 550 °C was 2.049, which is close to the value for single crystals of lithium tantalate (2.176).