The contribution of thin PFPE lubricants to slider-disk spacing

We have investigated the effect of the molecular weight (MW) and film thickness of a perfluoropolyether lubricant, Zdol, on the slider-disk spacing loss, or clearance. The major conclusion of this work is that Zdol films as thin as 10 Angstrom can reduce the slider-disk clearance by 2 nm or more in the molecular weight range of 1000-5000 amu. This is attributed to the attractive van der Waals interaction between the slider and the disk surface that causes the Zdol main chain to interact with the slider surface, giving rise to a friction force. When the film thickness of th a lubricant exceeds the monolayer thickness, dewetting can take place. The droplets that form occupy the space between the slider and disk surface reducing the slider-disk clearance by as much as similar to4 nm. There is a step increase in the acoustic emission signal at the dewetting thickness transition, indicative of a slider disk interference.