Based on the vital effect of the interfacial behaviors on tunneling magnetoresistance in Fe/MgO/Fe junctions, the thickness-dependent electronic structure of iron on MgO(111) films with {100} facets was investigated. The results illustrated that the chemical interaction at the interface of Fe and MgO films was rather weak. Instead, a upward band bending of MgO with 1.2 eV was obviously observed with the increase of Fe thickness. The particle size effect was responsible for these shifts of core levels owing to the three-dimensional growth of Fe. These results were further testified by the data from the lattice vibration in Fe-MgO system. (C) 2012 Elsevier B.V. All rights reserved.