Pressure Dependence of C–V Curve for Ferroelectric PbTiO3 Thin Films Prepared by RF Multi-target Magnetron Sputtering

Lead titanate thin films were prepared in-situ by RF magnetron sputtering method in the substrate temperature region of 550 °C ? 650 °C using Ti and Pb metal targets and oxygen gas. The films deposited at 650 °C for 60 min – when the applied power to the Ti and Pb target and deposition pressure were 200 W, 40 W, and 1.8 × 10^?2 Torr, respectively — had stoichiometric composition ratio and shown X-ray diffraction patterns of tetragonal structure like that of the powder. For the application to the piezoelectric field effect transistor (PI-FET), the substrate of SiO₂ (50 nm)/p-Si(100) was used. Leakage current density of the thin film was 7 × 10^?8 A/cm² at 100 kV/cm, dielectric breakdown voltage was 1.8 MV/cm, and so it showed high insulator characteristics. Capacitance-voltage curve was measured as a function of pressure. The variation width of the capacitance was 6.5 pF at bias voltage of –4 volts, and the value increased linearly according to the pressure up to about 6 kgf/cm², and was saturated at the pressure of 8 kgf/cm².