Low-Temperature Preparation and Characterization of (Pb,Ba)TiO_3 Thin Film by Sol-Gel and Hydrothermal Treatment

摘要

(Pb,Ba)TiO_3 (PBT) films with the perovskite structure have been prepared by sol-gel and hydrothermal treatments at temperatures below 200℃. TiO_2 gel films were prepared on Pt/TiO_x/SiO_2/Si substrates dried at 150℃ and transformed into crystalline PBT and BaTiO_3 (BT) thin films by hydrothermal treatment in Ba(OH)_2-Pb(OH)_2 mixture and Ba(OH)_2 alkaline solutions. PBT thin films were crystallized under conditions in which Ba(OH)_2 concentration was higher than that of Pb(OH)_2. The surface structure and variation in composition of BT films subjected to hydrothermal treatment were evaluated by backscattered electron and secondary electron images. Crest areas at the center of grains in the BT thin films are composed of light elements, but heavy elements are distributed in the vicinity of the boundary. The number of islands created by hydrothermal treatment increase with increasing Ba(OH)_2 concentration; simultaneously, the degree of squareness of the P—E hysteresis loops of BT thin films degrades. PBT thin films treated at 200℃ for 3h in 0.15M (mol/l) Ba(OH)_2-0.10 M Pb(OH)_2 solution have polarization hysteresis loops with a high degree of squareness, and the polarization at zero electric field is 28 μC/cm~2.