We demonstrate that strontium titanate (Sr-Ti-O) thin films having A-site excess composition in perovskite structure deposited by pulsed laser deposition (PLD) under magnetic field show a spontaneously formed superlattice structure. The spontaneous superlattice formation mechanism is proved to be spinodal decomposition. Results show that the Sr-Ti-O thin films with spontaneously formed superlattice structure exhibit room-temperature ferroelectricity. The induced ferroelectricity is brought about by the strain along the out-of-plane direction, and is explained based on thermodynamic considerations.
- Naoki Wakiya
- Naonori Sakamoto
- Hisao Suzuki
