Ferroelectricity in ultrathin perovskite films

We report studies of ferroelectricity in ultrathin perovskite films with realistic electrodes. The results reveal stable ferroelectric states in thin films less than $10\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ thick with polarization normal to the surface. Under short-circuit boundary conditions, the screening effect of realistic electrodes and the influence of real metal-oxide interfaces on thin film polarization are investigated. Our studies indicate that metallic screening from the electrodes is affected by the difference in work functions at oxide surfaces. We demonstrate this effect in ferroelectric $\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_{3}$ and $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ films.