抄録
Heteroepitaxial BaTiO3 thin films were prepared by RF magnetron sputtering under various gas pressures ranging from 0.08 to 27 Pa. Influence of the gas pressure was investigated through characterization of X-ray diffraction analyses and ferroelectric properties of the epitaxial BaTiO3 films. When the substrates were placed at a position directly above the sputtering target and the epitaxial films were grown under lower gas pressures, the epitaxial films were crystallographically damaged and no ferroelectricity was observed due to ionic bombardment of particles which are generated at the surface of the target and accelerated by plasma sheath voltage. When the films were grown under higher pressures, the lattice misfit strain was relaxed and ferroelectric properties were degraded, because of a lack of assistance from the irradiated sputtering particles. Sputtering under intermediate gas pressure of 6.3 Pa resulted in optimized crystallinity and ferroelectric properties, in which lattice misfit strain and remanent polarization, 2Pr, were 5% and 43 μC/cm2, respectively. We concluded that control of energy and/or amount of the irradiated particles at the film surface during heteroepitaxial growth is essential to improve ferroelectric properties of BaTiO3 thin films.
