Influence of the ferroelectric polarization on the electronic structure of BaTiO3 thin films

Micron scale ferroelectric (FE) domains have been written into a 20-nm-thick epitaxial thin film of BaTiO3 (001) [BTO(001)] on a Nb-doped SrTiO3 substrate using a piezoforce microscope (PFM). The domain-dependent electronic structure has been studied using fully energy-filtered photoemission electron microscopy (PEEM) and synchrotron radiation. Shifts, induced by FE polarization, of up to 300 meV were observed in the work function of the sample. The surface is Ba-O terminated. Polarization-induced distortion of the electronic structure was observed in the valence band and on the Ba 3d, Ti 2p and O 1s core levels of BTO. Polarization-dependent surface adsorption was observed. A simple electrostatic model based on net surface charge is not sufficient to explain the observed modifications in the electronic levels. Copyright © 2010 John Wiley & Sons, Ltd.