EVALUATION OF VERY THIN LUBRICANT FILMS

Very thin films of perfluoroalkylpolyether (Rf) derivatives having benzene rings on carbon surfaces were evaluated using scanning tunnelling (STM) and frictional force (FFM) Microscopes. Two kinds of surface were used as substrates: one was highly oriented, pyrolytic graphite (HOPG) as a defect-free and inactive surface, and the other was sputtered carbon as an active surface having many defects. STM was used to observe the configuration and mobility of lubricant molecules and clusters on the HOPG. The STM images reveal that the lubricant molecules in clusters are not fixed but can easily change positions. FFM was used to evaluate frictional force characteristics on the non-lubricated and lubricated sputtered carbon films. On sputtered carbon film even the lubricants that had insufficient stability on HOPG proved to be stable and able to decrease the friction. The adsorption mechanism of a lubricant on a practical sliding surface that is active and has many defects, such as sputtered carbon, is different from that on a defect-free and inactive surface such as HOPG.