This study investigates the effects of thermal annealing on the MgxZn1-xO films. MgxZn1-xO films were deposited by a radio-frequency magnetron sputtering system using a 6 in. ZnO/MgO (80/20wt%) target. The Hall results, x-ray diffraction (XRD), transmittance, and x-ray photoelectron spectroscopy (XPS) were measured. The XRD results indicate that the appearance of only (111) peaks in the as-grown MgxZn1-xO film is a sign of the cubic single phase, whereas the appearance of ZnO (002) peaks in MgxZn1-xO films annealed at 700 and 800 C confirms the formation of a wurtzite single-phase crystal. The existence of a weak (002) -wurtzite peak besides the (111)-cubic peak indicates the coexistence of two phases. The absorption spectra of MgxZn1-xO annealed at 700 and 800 C show two stages at wavelengths of 357 and 261 nm. The XPS spectra of MgxZn1-xO films were also demonstrated. The results of this study show that the ZnO films were separated from MgxZn1-xO films after higher thermal annealing. c 2010 American Vacuum Society. [DOI: 10.1116/1.3442476]