(534a) Nanometer-Thick Fluorinated Ionic Liquids (ILs) As Media Lubricants in Hard Disk Drives

Nanometer-thick lubricants are important for nano- and micro-electromechanical systems (NEMS/MEMS) and hard disc drives (HDDs). Since ILs have smaller molecular size, higher thermal stability, tunable molecular structures, and layering structure when applied on solid surfaces as thin films, they are promising as the novel nanometer-thick lubricants. In the current study, an IL with imidazolium cations and fluorinated anions, [Bmim][FAP], and the state-of-the-art perfluoropolyether (PFPE), z-tetraol, were compared. Thermogravimetric analysis (TGA) indicated that [Bmim][FAP] showed higher thermal stability than z-tetraol, which is highly desirable in lubrication. The surface roughness, which is characterized by atomic force microscopy (AFM), indicated that the monolayer thickness (ML) of [Bmim][FAP] is only ~50% of that of z-tetraol, which can be attributed to the smaller molecular size of [Bmim][FAP]. The lower ML of [Bmim][FAP] over z-tetraol was further confirmed by the friction results. As the distance between the head and the media in a HDD is only ~10 nm, the lower ML is expected to increase the areal density. The friction coefficient of the nanometer-thick IL is slightly higher than that of the PFPE, which can be attributed to weaker bonding to the solid substrate and less fluorinated components in the molecular structure.