Self-polarization induced by lattice mismatch and defect dipole alignment in (001) BaTiO3/LaNiO3 polycrystalline film prepared by magnetron sputtering at low temperature

Upward self-polarization phenomenon was observed and studied in the highly (001)-oriented BaTiO3/LaNiO3 polycrystalline film, and the polycrystalline film was in situ prepared by radio frequency magnetron sputtering at 400 degrees C without post treatment. The low temperature crystallization and high orientation of BaTiO3 polycrystalline film may be caused by the better compatibility between BaTiO3 and LaNiO3. The upward self-polarization phenomena was characterized by piezoelectric force microscopy (PFM), and the coupling effects of low crystallization temperature, high (001) orientation, large compressive strain gradient and preferred orientation of defect dipoles are considered to be responsible for the upward self-polarization phenomena in the BaTiO3/LaNiO3 polycrystalline film during the cooling process, especially when ferroelectric domains nucleate and grow near 120 degrees C.