HEAT-INDUCED PHASE-SEPARATION OF SELF-ASSEMBLED MONOLAYERS OF A FLUOROCARBON-HYDROCARBON ASYMMETRIC DISULFIDE ON A AU(111) SURFACE

Heat-induced phase separation of fluorocarbon-hydrocarbon self-assembl ed monolayers (SAMs) on a Au(111) surface was studied by scanning tunn eling microscopy (STM), atomic force microscopy (AFM) and friction for ce microscopy (FFM). Phase-separated domains were depressed by 0.3 nm with a lateral dimension of 20-200 nm. The friction forces on the high er parts were smaller than those on the lower domains. The higher part s were assigned to the hydrocarbon chains, because the fluorocarbon ch ains should have a larger friction force acting on them than the hydro carbon chains against the silicon nitride tip. Phase separation sugges ts cleavaging of the S-S bonds of disulfides in the SAMs. XPS measurem ents clearly showed an increase in the isolated Au-S binding species, suggesting the existence of the thiolate (monomer).