  Micrometric domains of precise ferroelectric polarization have been written
into a 20 nm thick epitaxial thin film of BaTiO3(001) (BTO) on a Nb doped
SrTiO3 (STO) substrate using PiezoForce Microscopy (PFM). The domain dependent
electronic structure has been studied using fully energy-filtered PhotoEmission
Microscopy (PEEM) and synchrotron radiation. Shifts, induced by ferroelectric
polarization, of up to 300 meV are observed in the work function of the sample.
The surface is Ba-O terminated. Polarization-induced distortion of the
electronic structure is observed in the valence band and on the Ba 3d, Ti 2p
and O 1s core levels of BTO. Polarization dependent surface adsorption is
observed. A simple electrostatic model based on net surface charge is not
sufficient to explain the observed modifications in the electronic levels.
