Optimization of Pb content in a precursor solution for the fabrication of (Pb,La)(Zr,Ti)O₃ films for optical applications by chemical solution deposition

400-nm-thick (Pb,La)(Zr,Ti)O₃ (PLZT) films with a composition of Pb:La:Zr:Ti = X:3:65:35 were fabricated on (111)Pt/Ti/SiO₂/(100)Si substrates at 700°C by chemical solution deposition using precursor solutions with Pb contents of X = 107, 112, 116, 121 and 126. The PLZT films fabricated from the solutions of X = 107 and 112 had bimodal structure and included pyrochlore phase. The pyrochlore region decreased with increasing the Pb content, and single perovskite phase PLZT films with well-filled structure were obtained at the Pb contents of 121 and 126. From these results, we concluded that the Pb-content of X = 121 (125 mol% relative to a stoichiometric value) was optimum for the fabrication of PLZT films for optical applications. This optimization slightly improved electrical and electrooptic properties of the PLZT films, and finally the PLZT(121/3/65/35) film showed the Pockels coefficient of 84 pm/V.