Microstructural orientation, strain state and diffusive phase transition of pure argon sputtered BaTiO₃film

Highly (0 0 1)-oriented BaTiO 3 thin film was deposited on a LaNiO 3 buffered Si substrate by the pure argon sputtering method. X-ray diffraction analysis indicates that while the LaNiO 3 buffer layer is slightly tensile-strained, the upper BaTiO 3 layer is actually under an in-plane compressive strain state. The microstructure and crystallographic orientation of the BaTiO 3 film were further analysed by transmission electron microscopy and electron diffraction observations by in situ tilting the film sample in the vacuum chamber. Temperature dependent dielectric measurements demonstrate that the ferroelectric to paraelectric phase transition temperature is lowered to 108 °C, which is attributed to the hardening of the soft mode induced by the presence of the compressive strain state. Furthermore, the observed strongly frequency dependent dielectric dispersions and the validity of the Vogel–Fulcher relationship indicate that the pure argon sputtered BaTiO 3 thin film shows a diffusive ferroelectric phase transition.