Ab initio calculations of ferroelectric instability in PbTiO3 capacitors with symmetric and asymmetric electrode layers
Y. Umeno, J. M. Albina,
B. Meyer, C. Elsässer
Physical Review B, Band 80, Seiten 205122-1-205122-8 (2009)
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 Pt/PbTiO3/Pt, Pt/PbTiO3/SrRuO3, and SrRuO3/PbTiO3/SrRuO3 models. SrRuO3/PbTiO3/SrRuO3 capacitors with PbO-terminated PbTiO3 layers have a ferroelectric stability similar to that of Pt/PbTiO3/Pt, while the ferroelectricity is strongly suppressed in the capacitors with TiO2-termination. The asymmetric combination of the electrodes enhances the ferroelectric polarization pointing from SrRuO3 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 PbTiO3 to the SrRuO3 electrode by about 1.0 eV.