Friction and wear on the atomic scale

Friction force microscopy experiments have been performed under ultrahigh vacuum conditions. Within a small force regime (below 1 nN), friction without wear is observed as a function of velocity on ionic crystals and metals. The results are discussed in the framework of a refined version of the Tomlinson model, which includes thermal activation. Higher normal forces lead to abrasive wear. The debris extracted from ionic crystals can be characterized with high lateral resolution. The dependence of wear rate on velocity and normal force is investigated.