Structural and electrical properties of KNbO3 thin film grown on a Pt/Ti/SiO2/Si substrate using the RF magnetron sputtering method

A homogeneous KNbO3 (KN) thin film was grown on a Pt/Ti/SiO2/Si substrate using the RF sputtering method. A K2.88Nb5O15 secondary phase was formed in the KN film when the deposition and the annealing temperatures were greater than room temperature (RT) and 800 °C, respectively, owing to the evaporation of K2O. On the other hand, KNb3O8 and K3Nb5.45O15 secondary phases were formed in the KN films when the annealing temperature was less than 800 °C or the annealing time at 800 °C was shorter than 90 min. A homogeneous KN thin film was formed when it was deposited at RT and subsequently annealed at 800 °C for 90 min under the K2O atmosphere. This KN film exhibits a relative permittivity of 884 with a dissipation factor of 6.71% at 100 kHz. The leakage current density of 1.06 × 10−6 A/cm2 at 0.1 MV/cm and a breakdown field of 1.5 MV/cm were observed from this film. This film showed a saturation polarization of 21.9 μC/cm2, with a remnant polarization of 8.3 μC/cm2, and a piezoelectric strain constant of 125 pm/V.