Ferroelectric and Pyroelectric Properties of Sol-Gel Derived PbCaTiO3 Thin Films Using Low-Temperature Annealing

Abstract

PCT7030 (Pb0.7Ca0.3TiO3, PCT7030) films have been prepared by a sol-gel method on platinum-coated Si substrate. PCT7030 films were treated at different radiation densities using CO2 laser annealing to obtain good ferroelectric properties without causing thermal deterioration of the underlying layer. In addition, metallic oxide LaSrMnO3 buffer layer was employed to improve the electrical properties of PCT7030 films. From XRD measurements, we found that fully perovskite phase of PCT7030 films could be obtained at a radiation density below 572 W/cm2. On the other hand, perovskite phase of PCT7030 films with co-existing TiOx were observed for specimens treated at a higher radiation density. The correspondent P-E curves of PCT7030 films with entirely perovskite phase exhibited saturated hysteresis loops and the specimens possessing perovskite PCT7030 and co-existing TiOx phase showed serious leakage. Microstructural investigations imply that grain size increases with increasing radiation density, and voids may evolve on the grain boundaries when high radiation density was employed, indicating that atomic species evaporation of PCT7030 films or coarsening-induced voids may be produced at an over-annealing condition and therefore electrical properties were deteriorated. In the pyroelectric measurement, pyroelectric coefficient of CO2 laser-annealed PCT7030 films varied as a function of calcium content and a pyroelectric coefficient maximum were obtained at a composition near PCT7030, indicating that low temperature laser-annealing process can be employed in ferroelectric and pyroelectric thin film preparation.