Surface electronic structure of polar NiO(111) films

The surface and electronic structure of polar NiO(111) films with or without facets, prepared on a Mo(110) substrate, were in situ studied using various surface analytical techniques. A new surface state located at 0.8–1.8 eV measured by electron energy loss spectroscopy was observed on faceted NiO(111) films, which is originated from surface Ni vacancies. This surface state is decreased by annealing or deposition of Ni atoms. The experimental results indicate that the charge transfer occurs between surface and bulk of the faceted NiO(111) films. Present work provides a model surface with polarity and facets, which can be used for further investigation on chemical adsorption of atoms or molecules as well as selective reaction.