Ninety degree domains in RF-sputtered BaTiO3 thin films on platinum substrates

We report 90 degrees domains in (110)-oriented polycrystalline BaTiO3 thin films. The domain and crystal structures of the thin films were investigated using transmission electron microscopy and high temperature X-ray diffraction, respectively. From X-ray diffraction, it was found that the prepared films had a (110)-preferred orientation and a tetragonal structure at room temperature. Observation in the plan-view and cross-sectional modes using transmission electron microscopy clearly indicated the presence of a 90 degrees domain structure. In the cross-sectional mode, a 90 degrees domain structure was observed along the film growth direction and in the plan-view mode, it was also found that a 90 degrees domain boundary was initiated from the (111) twin boundary. The formation of a 90 degrees domain boundary was discussed in terms of planar defects such as the (111) twin and we also proposed two kinds of stress relief mechanisms induced by 90 degrees domain formation.