Preparation of c-axis oriented PbTiO3 thin films and their crystallographic, dielectric, and pyroelectric properties

Highly c-axis oriented and epitaxial PbTiO3 thin films were grown on MgO single crystals and epitaxial Pt film substrates by the rf-magnetron sputtering method. The films with a 98% c-axis orientation rate were obtained under low deposition rate (<20 Å/min) and low gas pressure (∼1 Pa) using a PbO-rich target. Phase transition of the PbTiO3 thin film was studied by high-temperature x-ray diffraction. It was found that the c-axis of the tetragonal phase was parallel to the substrate just below Tc and the c-axis becomes perpendicular to the substrate with lowering of temperature. These films show high resistivity (∼1010/Ω cm). It was found that significant pyroelectric currents are detected on all specimens without poling treatment. The polarization directions of the films are the same in all specimens. One of these films had a low relative dielectric constant of 97 and a high pyroelectric coefficient of 2.5×10−8 C/cm2 K without poling treatment. These films will be suitable for applications such as pyroelectric infrared detector and piezoelectric transducer.