Direct spectroscopic evidence of charge reversal at the Pb(Zr 0.2Ti0.8)O3/La0.7Sr 0.3MnO3 heterointerface

At the heterointerface of a top ferroelectric Pb(Zr0.2Ti 0.8)O3 (PZT) ultrathin film and a bottom La 0.7Sr0.3MnO3 (LSMO) electrode, we used continuous synchrotron-radiation photoelectron spectroscopy to probe in situ and demonstrated that the interfacial charges are reversible and their affected valence-band barrier height becomes modulated upon switching the polarization in the top layer. By monitoring the core-level shifting of the buried LSMO layer under continuous illumination of synchrotron radiation, we directly observed a temporal screening of polarization induced by the photon-generated carriers in the top PZT layer. This dynamic characterization of the core-level shifting of the buried layer demonstrates an effective method to probe the electric conduction and ferroelectric polarization of an ultrathin ferroelectric oxide thin film. © 2011 American Physical Society.