Polarization dependence of Schottky barrier heights at interfaces of ferroelectrics determined by photoelectron spectroscopy

Ferroelectric polarization in thin films is stabilized by screening charges in the metal electrodes. Imperfect screening of the polarization charge strongly modifies the film's capacitance and should lead to a variation of the Schottky barrier height at the interface with polarization direction. An experimental approach based on photoelectron spectroscopy is introduced which allows us to quantitatively determine Schottky barrier heights at ferroelectric/metal interfaces in dependence on polarization. The procedure is exemplified for BaTiO₃ single crystals with RuO₂ and Pt electrodes, revealing a variation of Schottky barrier height of $1.1$ and $0.65$ eV in dependence on polarization for RuO₂ and Pt electrodes, respectively. Inhomogeneous barrier switching is observed for Pt electrodes, which may be related to defect formation during metal deposition.