Pulsed-Laser Deposition of Ferroelectric NaNbO3 Thin Films

High-quality NaNbO3 (NN) thin films were epitaxially grown on a (100)SrTiO3 substrate by pulsed-laser deposition. NN films with a flat surface morphology were obtained, when the films were grown slowly at high substrate temperatures, high oxygen partial pressures, and low laser energy densities. In order to characterize their dielectric properties, the NN films were epitaxially grown on (100)SrRuO3∥(100)SrTiO3 substrates. The relative dielectric constant, ε r, and dielectric loss, tan δ of the film were 252 and 0.03 at 1 kHz, respectively. When the temperature dependence of ε r was measured, ε r was found to suddenly increase at 377°C, which corresponds to the transition temperature of NN between the antiferroelectric and paraelectric phases. The P–E hysteresis loop of the NN films exhibited characteristic ferroelectric behavior.