Scanning-force microscopy study of surface morphology and frictional properties of synthetic lubricant assemblies on a substrate

Using simultaneous atomic force microscopy (AFM) and lateral force microscopy (LFM), we have examined the morphology of lubricant assemblies on a substrate, and have evaluated the relative friction forces over the lubricated and bare substrate surfaces. The lubricant was synthesized in house, and was coated onto a thin carbon film on a glass substrate by a dip-coating technique. For a substrate with an appropriate amount of the lubricant prepared under a well-controlled coat procedure, the LFM image clearly revealed the existence of island-like structures of the self-assembled lubricant molecules, which the AFM image showed only ambiguously. Careful analysis of the friction force loops during the individual friction scanning revealed that the friction forces over the lubricated domains were actually lower than those over the unlubricated domains.