Na0.5Bi0.5TiO3-based ferroelectric thin films

Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) is considered to be an excellent candidate for a lead-free piezoelectric material from the viewpoint of environmental protection. The optimum temperature of crystallinity is 650 degrees C. The films exhibit a well-defined hysteresis loop with a remnant polarization 2Pr of about 1 mu C/cm(2) and a coercive voltage V-c of approximately 0.9V. The films also show good insulating property at room temperature. The high frequency C-V curve is indicative of good film/substrate interface characteristic. The fixed charge density (N-fc) and the surface state density (N-ss) are considered to be adequate for a ferroelectric field effect transistor operation. Electrical measurements results show that this kind of films have a potential practice for device applications such as memory and switching devices.