Abstract
A novel method for identifying the adhesion force and the dynamic elongation of molecularly thin lubricant coated over DLC surface was developed while an SPM tip retracting from contact position by using transient response of the SPM cantilever arising after separation. The accuracy of measurement of the cantilever displacement was considerably improved by mounting a silicon tip with optically reflecting surface on the cantilever to produce high quality image of the interference fringe pattern formed by Michelson interferometry. To describe experimental transient response, a model for separation process was introduced wherein the surface force decreases from an initial value (contact force) to zero in proportion to the tip travel accompanying elongation of the lubricant. Calculated vibration waveforms using this model were found to be in good agreement with observed waveforms. This hinted that PFPE thin film could stretch as much as a hundred times of lubricant thickness.
