Lead-free (Bi0.5Na0.5)TiO3-based thin films by the pulsed laser deposition process

We have studied the effect of deposition parameters on the microstructure, crystallinity, and ferroelectric properties of 0.88(Bi_0.5Na_0.5)TiO₃-0.08(Bi_0.5K_0.5)TiO₃-0.04BaTiO₃ thin films grown on SrRuO₃-coated SrTiO₃ substrates by pulsed laser deposition. The parameters studied were the repetition rates, substrate temperatures, oxygen pressures, and laser energies. It was realized that the films prepared at 800°C, 10 Hz, 400 mtorr, and 1.2 J·cm^-2 exhibited the highest ferroelectric properties. The measured remanent polarization, dielectric constant at 1 kHz, and coercive field for this film were about 30 μC·cm^-2, 645, and 85 kV·cm^-1, respectively. Increasing the oxygen pressure during deposition from 200 to 400 mtorr improved the crystallinity, microstructure, dielectric constant, and polarization of the films. The leakage current and dielectric loss were suppressed at 400 mtorr because of the lower concentration of oxygen vacancies and disappearing pinholes and surface undulations in the film deposited at this pressure.