Interface effect on the magnitude and stability of ferroelectric polarization in ultrathin PbTiO₃ films from first-principles study

The interface effects on the ferroelectric polarization and stability of PbTiO₃ (PTO) films with metallic (Pt) or oxide (LaNiO₃, SrRuO₃) electrodes were studied using density functional theory calculation. It was found that the PTO film with oxide electrodes has stronger electrode/ferroelectric interface adhesion, lower polarization magnitude, and worse polarization stability, than that with Pt electrode. The PbO-terminated PTO films show weaker adhesion with the electrodes, but have higher polarization magnitude and better polarization stability than the TiO₂-terminated ones. The strain effects induced by misfit interface were also studied. Results show that the ferroelectric polarization and its stability can be enhanced by applying compressive strain, while depressed by applying tensile strain.