The Ge doped ZnO films were deposited on quartz substrates by radio frequency magnetron sputtering. The effects of doping and substrate temperature on the structural and optical properties of the Ge doped ZnO films were investigated by means of X-ray diffraction (XRD), UV-visible transmission spectra, X-ray photoelectron spectroscopy and photoluminescence (PL) spectra. The XRD patterns showed that Zn(2)GeO(4) phases were formed in the films. With the increase of substrate temperature the crystallization of Zn(2)GeO(4) was improved, and that of ZnO phases turned worse, and no diffraction peak of ZnO was observed when the substrate temperature was 700 degrees C. Obvious ultraviolet (UV) light emission was found due to ZnO grains, and it was much stronger than that of un-doped ZnO films. The enhancement of UV light emission at about 380 nm may be caused by excitons which were formed at the interface between Zn(2)GeO(4) and ZnO grains. In the visible region of the PL spectra, the green light emission peak of samples at about 512 nm was associated with defects in ZnO. A red shift of the green light emission peak was observed which can be explained by the fact that there is a luminescence center at about 548 turn taking the place of the defect emission of ZnO with the increase of substrate temperature. The red shift of the green light emission peak and the 548 nm green light emission peaks of the PL spectrum show that some Ge(2+) should replace the Zn(2+) positions during the Zn(2)GeO(4) grains growth and form the Ge(2+) luminescence centers in Zn(2)GeO(4) grains. (C) 2009 Elsevier B.V. All rights reserved.