AFM study of polymer lubricants on hard disk surfaces

Abstract

Thin liquid films of PFPE (perfluoropolyether) lubricants dip-coated on hard disk surfaces were imaged with non-contact mode AFM. Demnum lubricants with phosphazene additives exhibited strong interactions with a silicon tip due to the formation of liquid bridges between the lubricants and the tip, as indicated by a remarkable hysteresis loop between approach and retraction curves in force vs. distance measurements. Features resulting from capillary forces due to tip tapping to the lubricants were revealed, which demonstrated that the capillary forces could be used to lock the non-contacting tip at a certain separation from the substrate surface to obtain AFM images. Force vs. distance curves for Fomblin Z-dol lubricants showed negligible hysteresis effects and features corresponding to lateral distortion of the tip by the lubricants only were observed. In both cases, only when the tip was positioned far above the surfaces could the natural distributions of the lubricants be imaged. © 1998 Springer-Verlag.