Effect of Heat Treatment Temperature on PFPE Molecules Bonded on DLC Surface

Based on the demand of extremely increased area density for magnetic data storage, the contact recording systems have been proposed, in which stronger and thinner hard coatings and lubricant films for the head disk interface (HDI) are desired. In this study, two lubrication methods, i.e., the vacuum vapor deposition and dip-coating methods are evaluated and compared in order to satisfy the demands from the HDI development. Perfluoropolyether (PFPE) is applied to the diamond-like carbon (DLC) surface. The advantage of the vacuum vapor deposition is to prevent contamination of the DLC surface from the atmosphere because of no exposed samples to the atmosphere. In contrast, the advantage of dip-coating method is to thicken the bonded layer of the PFPE by heat treatment. We discuss the adsorption mechanism between the PFPE molecules and DLC surface for each method. In addition, a simple reaction model based on the Arrhenius equation is developed and compared to the experimental results. We concluded that the reaction will be dominated by covalent bonds and hydrogen bonding. Furthermore, the reaction model can well express the experimental results. The remarkable destruction of the DLC film by the heat treatment are not seen in the samples heat treated at a temperature from 353 to 423 K while the remarkable destruction are seen in the samples treated from 423 to 473 K.