Polycrystalline RbTiOPO4 and KTiOPO4 bilayer thin films by spray pyrolysis

A novel titanium precursor has been used with spray pyrolysis (SP) to deposit polycrystalline rubidium titanyl phosphate, RbTiOPO4 (RTP), thin films on thin film potassium titanyl phosphate, KTiOPO4 (KTP), for possible waveguide applications. The titanium precursor for this process was titanium peroxo-hydroxo complex (TPH) in aqueous diluted HNO3. The morphology of thin films of RTP and KTP depended on the deposition conditions. Low deposition rates provided thin (under 1 mu m) films that were uniform and smooth. The optical absorption of RTP thin films grown on quartz substrates indicated the film was transparent above 350 nm and no changes in absorption were detected upon annealing at temperatures at or below 750 degrees C. The resistivities of the thin-film RTP and KTP were above 10(8) Ohm m. Hall effect measurements indicated that the free carrier concentration and mobility for the thin-film KTP and RTP samples were higher than 10(13)-10(14) m(-3) and lower than 0.0001 m(2) V-1 s(-1), respectively. Gray pits, corresponding to the well-known 'gray tracks' in single-crystal KTP, were left in thin-film KTP samples after high laser power irradiation at 266 nm. The XRD measurements revealed that RTP thin films began to crystallize at 700 degrees C to give non-oriented crystals. The as-deposited films dissolved in warm diluted HCl more rapidly than the annealed ones. (C) 1998 Elsevier Science S.A. All rights reserved.