Micro wear tests by using atomic force microscope: relationship between contact area and pull-off force

摘要

Single asperities were formed on a single-crystal gold plate and the asperities were rubbed with a silicon leaf spring attached to an AFM (atomic force microscope). A focused ion beam (FIB) system was used to form gold pyramid-shaped asperities on the surface of a single-crystal gold plate. The FIB was also used to create the two types of single crystal silicon leaf springs tested here; parallel and single. The pull-off force increased monotonically with sliding distance for each spring. For the parallel leaf spring, the pull-off force was proportional to the worn area of the gold asperity peak (measured by using an ordinary AFM probe) and was not affected by the ambient relative humidity. For the single leaf spring, the increasing rate of the pull-off force decreased with the larger worn area. The volume change of the gold asperity by rubbing was investigated quantitatively by using the AFM topography data. The result showed that total volume hardly changed, because a ploughing wear was probably taking place between micro silicon asperities on the spring and the gold asperity.