The flow of thin lubricant films on rotating disks

In this paper we report a study on the flow of thin viscous lubricant films on the surface of rotating silicon disks. The lubricant studied is a low molecular weight linear-chain perfluoropolyether polymer, Demnum S20, deposited in films 4-25 nm thick. The disks are spun at high speeds and the thickness profiles of the lubricant films are measured as a function of spin time by ellipsometry. Comparison of the measured thickness profiles with the theory of Emslie, Bonner and Peck, (J. Appl. Phys., 29 (1958) 858) shows that the flow of these thin lubricant films can be modelled as that of a continuum, newtonian liquid with a viscosity 50%-80% higher than that of bulk liquid. The increase above bulk viscosity may be attributed to molecular collective-motion effects or to an immobile molecular monolayer that does not flow with the rest of the film. © 1993.