Pyroelectric property of Pb5Ge3O11 thin films prepared by laser ablation

Pb5Ge3O11 films were prepared by laser ablation, and pyroelectricity was obtained in the films after annealing. Stoichiometric films were formed at oxygen pressures around 0.5 Torr during deposition. It was found that an unreported precursor phase was grown on Pt/Ti/SiO2/Si substrates at a temperature of 520 C. Subsequent annealing at 500 C for 2 h in air made it possible for the film to have (001) oriented texture of ferroelectric Pb5Ge3O11. This sample showed remanent polarization of 1.4 micro-C/sq cm with a ferroelectric hysteresis loop of an asymmetric shape and a pyroelectric coefficient of 4.3 nC/sq cm K, while these values were about one third of those reported for single crystal Pb5Ge3O11 in a polarization direction. The inferiority in this ferroelectricity is thought due to the lead-deficient phase involved in the film. Although this localized second phase still remains, the appreciable reduction in the process temperature for texturing a Pb5Ge3O11 film in the c-plane as low as around 500 C is attributed to the sufficient supply of oxygen during the deposition. (Author)