To investigate the influence of symmetric and asymmetric electrode layers on ferroelectric properties of perovskite capacitors, ab initio calculations based on density-functional theory using the local density approximation and the mixed-basis pseudopotential method are performed for $\text{Pt}/{\text{PbTiO}}_3/\text{Pt}$, $\text{Pt}/{\text{PbTiO}}_3/{\text{SrRuO}}_3$, and ${\text{SrRuO}}_3/{\text{PbTiO}}_3/{\text{SrRuO}}_3$ models. ${\text{SrRuO}}_3/{\text{PbTiO}}_3/{\text{SrRuO}}_3$ capacitors with PbO-terminated ${\text{PbTiO}}_3$ layers have a ferroelectric stability similar to that of $\text{Pt}/{\text{PbTiO}}_3/\text{Pt}$, while the ferroelectricity is strongly suppressed in the capacitors with ${\text{TiO}}_2$-termination. The asymmetric combination of the electrodes enhances the ferroelectric polarization pointing from ${\text{SrRuO}}_3$ to Pt while the opposite polarization becomes less stable. The epitaxial lattice strain does not strongly affect the electronic Schottky barriers of the symmetric capacitors. The contribution of the electrical field originating from the asymmetric electrodes influences the Schottky barriers significantly. The switching of the polarization in the asymmetric capacitor changes the Schottky barrier height from ${\text{PbTiO}}_3$ to the ${\text{SrRuO}}_3$ electrode by about 1.0 eV.

• Received 12 August 2009

DOI:https://doi.org/10.1103/PhysRevB.80.205122