Pyroelectric property of Pb5Ge3O11 thin films prepared by laser ablation
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Pb 5 Ge 3 O 11 films were prepared by laser ablation, and pyroelectricity was obtained in the films after annealing. Stoichiometric films were formed at oxygen pressures around 5 x 10 -1 Torr during deposition. It was found that an unreported precursor phase was grown on Pt/Ti/SiO 2 /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 Pb 5 Ge 3 O 11 . This sample showed remanent polarization of 1.4 μC/cm 2 with a ferroelectric hysteresis loop of an asymmetric shape and a pyroelectric coefficient of 4.3 nC/cm 2 K, while these values were about one third of those reported for single crystal Pb 5 Ge 3 O 11 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 Pb 5 Ge 3 O 11 film in the c-plane as low as around 500°C is attributed to the sufficient supply of oxygen during the deposition.