The current status of tribological surface science

Use of the ultrahigh vacuum methods of surface science allows the preparati on and study of highly characterized solid-solid interfaces for tribologica l investigations. One of the limiting factors in the progress of our unders tanding of tribology has been the inability to generate solid-solid interfa ces with well-defined, reproducible, atomic scale structures and compositio ns. The preparation of single crystalline surfaces of metals and the charac terization of adsorbed molecules on these surfaces has been one of the majo r accomplishments of the field of ultrahigh vacuum surface science. Combini ng surface science instrumentation with an ultrahigh vacuum tribometer has made it possible to bring to the study of tribology the same quality of exp erimental measurement as is available for many other surface phenomena. One phenomenon that has been explored in great detail is the effect of the cov erage of adsorbed species on friction between metal surfaces. Other measure ments have included the study of friction anisotropy; the effect on the fri ction between two single crystal surfaces of their relative crystallographi c orientations across the sliding interface. Finally, recent results have c orrelated the friction between adsorbate covered surfaces with the desorpti on energy of the adsorbed molecules. These results and measurements anticip ated for the future offer the opportunity to address truly fundamental ques tions in tribology and complement many of the other new tools recently deve loped for the study of tribological phenomena.