The surfaces of sputtered zinc oxide (ZnO) films and its interfaces with US are investigated with X-ray photoelectron spectroscopy and soft X-ray photoelectron spectroscopy measured at the synchrotron radiation facility BESSY II. Cadmium sulfide (CdS) films are prepared by thermal evaporation from the compound and the zinc oxide films by DC magnetron sputtering from an undoped zinc oxide target at low power densities with and without addition of oxygen to the sputtering gas. ZnO films deposited at room temperatures show an additional oxygen component located at the surface that can be mostly removed by heat treatment. The electronic interface properties are studied in dependence to ZnO deposition conditions. (C) 2003 Elsevier Science B.V. All rights reserved.