Tribo-assisted reorientation of nanometre-thick Ag film in ultrahigh vacuum environment

Abstract

The tribo-assisted reorientation of the 5-nm-thick Ag film with polycrystalline structure has been studied in an ultrahigh vacuum (UHV) environment. The film was prepared on an Si (1 1 1) √3 × √3-Ag surface in a UHV condition at a pressure less than 4 × 10−8 Pa. The friction coefficient of the film was 0.07 at the beginning of the sliding and decreased to 0.02 as the reciprocal sliding cycle proceeded. Reflection high-energy electron diffraction observation showed that the crystallographic orientation of the film surface was changed by the mechanical rubbing motion of the diamond pin. Scanning tunnelling microscopy observation showed that the Ag (1 1 1) plane on the worn surfaces of the film oriented parallel to the substrate surface. Synchrotron orbital-radiated X-ray diffraction showed that the Ag (1 1 1) domains in the layer increase as the number of slidings increase, which corresponded to the friction reduction process. This study has clarified the reorientation process of the Ag film with nanometric thickness.