The nanotribological properties of Zn0.75Mg0.25O grown on R-plane sapphire using metal-organic vapor-phase epitaxy at different substrate temperatures (RT, 600, 700 and 800 °C) were investigated. A slight sliding track was observed at ramped loads of 250 μN, and an obvious bulge edge surrounding the groove was observed at ramped loads of 1 000 μN. Because of the annealing treatment, all the Zn0.75Mg0.25O coatings showed a reconstruction phenomenon of crystallites. The volumes of the bulge edges were as high as 30% in the annealed specimens and were larger than the volumes of the RT-treated specimens when ramped loads of 1 000 μN were applied. Under frictional loading, atomic force microscopy examination of scratch-tested films indicated lower bonding forces on R-plane sapphire than M-plane sapphire.