Formation and modification of Schottky barriers at the PZT/Pt interface

A determination of the Schottky barrier height at the interface between ferroelectric Pb(Zr, Ti)O-3 thin films and Pt by photoelectron spectroscopy is presented. Stepwise Pt deposition was performed in situ onto a contamination-free Pb(Zr, Ti)O-3 thin film surface. The substrate surface is reduced in the course of Pt deposition as evident from the observation of metallic Pb. The Fermi level is found at E-F - E-VB = 1.6 +/- 0.1 eV above the valence band maximum of the as-prepared interface. Annealing of the sample in an oxygen pressure of 0.1 and 1 Pa strongly reduces the amount of metallic Pb and leads to a reduction in the Fermi level position at the interface to E-F - E-VB = 1.1 +/- 0.1 eV. Storage in vacuum at room temperature strongly reduces the interface leading to a significantly higher Fermi level position (E-F - E-VB = 2.2 +/- 0.1 eV). The reduction is attributed to the presence of hydrogen in the residual gas. The change in barrier height might be a severe issue for stable device operation with Pt contacts even at ambient temperatures.