Behavior of ultrathin liquid lubricant films for contact sliders in hard disk drives

Abstract

In this paper, we describe the behavior of ultrathin liquid lubricant films for contact sliders in hard disk drives. In the experiments, the ultrathin liquid lubricant film behavior is investigated using Zdol and cyclotriphosphazene-terminated PFPE lubricant which have different end groups as a function of lubricant film thickness. The disks are examined with a scanning microellipsometer before and after contact slider experiments. It is found that the lubricant film thickness profiles almost do not change, when the lubricant film thickness is less than one monolayer. It can also be observed that lubricant film thickness instability due to dewetting occurs as a result of slider-disk contacts for the tested lubricants and the films undergo spontaneous redistributions, resulting in significantly nonuniform film thickness profiles, when the lubricant film thickness is thicker than one monolayer. In addition, it is found that the observed behavior of ultrathin liquid lubricant films for cyclotriphosphazine-terminated PFPE lubricant contrasts markedly with that for Zdol. The difference between cyclotriphosphazene-terminated PFPE lubricant and Zdol is only the functional end group. Therefore, it may be concluded that their unstable lubricant behavior depends on the chemical structure of functional end groups.