FRICTION FORCE MICROSCOPY ON WELL-DEFINED SURFACES

Friction force microscopy is implemented in ultrahigh vacuum condition s, Atomic-scale friction is observed on clean surfaces. The onset of a tomic-scale stick-slip is observed and discussed in relation to the pl ucking model. Comparative measurements of AgBr(001) versus NaCl(001) a nd C-60 versus NaCl(001) demonstrate the material-specific contrast of friction. Contrast mechanisms are discussed in relation to these expe riments. The role of the chemical nature of the tip is exemplified for the case of Si(111) 7 x 7, where wearless sliding is achieved with a PTFE-coated probing tip.