The morphology and surface electronic structure of indium nitride films grown by plasma-induced molecular beam epitaxy have been studied using atomic force microscopy as well as X-ray and ultraviolet photoelectron spectroscopy. Valence band and In4d core level spectra were measured as a function of excitation energy (He I, He II and A1K alpha radiation) on samples with minimised exposure to ambient conditions after growth (30 s). A work function of 4.1 eV was determined and the onset of the valence band is located 1.6 eV below the Fermi level which is a strong indication of the already discovered electron accumulation at InN surfaces. In addition, the theoretically predicted InN valence states were observed. At the outermost InN surface the In4d level seems to consist of two components, where the existence of a metallic phase can be ruled out by a comparison with sputtered InN samples and measurements performed on an indium foil. (c) 2007 Elsevier B.V. All rights reserved.