A series of. Zn1-xMgxO thin films with various deposition temperatures were prepared on.sapphire(0 0 0 1) substrates by radio frequency (rf) magnetron co-sputtering with ZnO and Mg targets. The Mg contents in Zn1-xMgxO films were controlled by the deposition temperature. Through transmittance measurements, it was observed that the shift of the absorption edge depended on the deposition temperature due to the difference in the surface diffusion of the deposited Mg atoms. Furthermore, the film deposited at 600 degreesC exhibited the absorption edge at 289 nm resulting in the bandgap widening to 4.28 eV. From the X-ray diffraction (XRD) results, it was observed that all the films exhibited only the (0 0 0 2) peaks indicating the single-phase Zn1-xMgxO without changing the wurtzite structure of ZnO. The dependency of crystalline quality and surface morphology of the Zn1-xMgxO films on the deposition temperature was discussed. (C) 2003 Elsevier B.V. All rights reserved.