An ion layer gas reaction (ILGAR) technique for the deposition of thin metal oxide films such as zinc oxide has been developed. In a cyclic process a solid precursor layer was applied on a substrate by dipping in a Zn(ClO4)(2) solution and subsequent drying. Reaction with gaseous NH3/H2O led to a hydroxide layer which is thermally dehydrated to ZnO. The steps were repeated until the desired layer thickness was obtained. Under optimized conditions the chlorine remainder lay below 0.3 at%. X-ray-diffraction revealed a preferred orientation concerning the (002) plane. The band gap was determined to E-gap = 3.38 eV. First ZnO/CIGSSe solar cells showed efficiencies of 10.7%. (C) 2001 Elsevier Science B.V. All rights reserved.