Wear rate of vertically grown ZnO nanowires sliding against steel micro-sphere

In this work, ZnO nanowires were grown on Si(1 0 0) wafer and sapphire(0 0 1) substrates using metal-organic chemical vapor deposition (MOCVD). The morphology and crystal structure of ZnO nanowires were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The wear characteristics of ZnO nanowires were measured using an atomic force microscopy (AFM) apparatus. A steel micro-sphere (radius of 12 μm) was attached to the end of the AFM cantilever and slid against the ZnO nanowires using low normal load. The wear rate of ZnO nanowires was quantified by comparing the geometrical shape of ZnO nanowires before and after the wear test. Also, the adhesive force between the sphere and the nanowires was measured before and after the wear test. The increase of adhesive force is due to the increase in contact surface after the wear test.