Influence of ferroelectric order on the surface electronic structure of BaTiO3 films studied by photoemission spectroscopy

Abstract

The electronic structure of in situ grown ferroelectric BaTiO3(001) films is studied by angle-resolved photoemission spectroscopy. A two-dimensional state is found at the film-vacuum interface with an unexpected checkerboardlike Fermi surface. The observed absence of in-plane dispersion of the states is attributed to the influence of the strong electric fields of the ferroelectric bulk of the film. These fields cause Bloch oscillations and Wannier-Stark localization of free charges in real space, resulting in a smearing in reciprocal space. It is shown that this effect extends to thin SrTiO3 overlayers grown on the BaTiO3 film.