ON LIQUID-FILM THICKNESS MEASUREMENTS WITH THE ATOMIC-FORCE MICROSCOPE

We provide a theoretical description of some recent measurements where the thicknesses of solid-supported thin lubricant films are measured using the atomic-force microscope [Mate et al., J. Chem. Phys. 90, 7550 (1989)]. In our model, the differences observed between the thicknesses measured with the force microscope and ellipsometric thicknesses are explained by the appearance of an instability in the liquid film. Our calculations also predict the dependence of these differences on the thickness of the film.