Electrical Properties of a 0.95(Na _0.5 K _0.5) NbO ₃-0.05 CaTiO ₃ Thin Film Grown on a Pt / Ti / SiO ₂/ Si Substrate

An amorphous phase was formed in a 0.95(Na_0.5K_0.5)NbO₃-0.05CaTiO₃ (NKN-CT) film grown at 300°C, and a low-temperature transient Ca₂Nb₂O₇ phase was formed in the film grown at 500°C. In films grown at high temperatures (≥600°C), secondary phases such as K_5.75Nb_10.85O₃₀ and K₄Ti₁₀Nb₂O₂₇ were developed without the formation of a NKN-CT phase, probably because of Na₂O evaporation. The same secondary phases were formed in the film grown at 300°C and subsequently annealed at 850°C under an air atmosphere. However, a homogeneous NKN-CT phase was formed in films grown at 300°C and subsequently annealed at 830°C-880°C under the K₂O and Na₂O atmospheres. Moreover, the film annealed at 830°C in particular exhibited good electric and piezoelectric properties, including a high dielectric constant of 747 with a low dissipation factor of 0.93% at 100 kHz, low leakage current density of 2.0 × 10^-7 A/cm² at 0.1 MV/cm, and high P_r and d₃₃ values of 15.4 μC/cm² and 124 pm/V at 100 kV/cm, respectively.