Humidity effects on PFPE lubricant bonding to a-CHx overcoats

The continued reduction in the head-disk separation of magnetic data storag e systems and the corresponding increase in the frequency of head-disk cont acts will place severe stress on the lubricant and overcoat used to protect the surfaces of magnetic media. With decreasing fly heights, environmental conditions such as temperature and humidity that influence the lubricant-o vercoat interactions become increasingly important to the tribological perf ormance of the head- disk interface. It is essential to obtain a fundamenta l understanding of the molecular interactions at the lubricant-overcoat int erface in order to maintain the reliability of future hard disk drives. The coadsorption of model fluoro alcohols and fluoro ethers with water was stu died to gain a fundamental understanding of the effects of humidity on the bonding of perfluoropolyalkyl ether (PFPE) lubricants to amorphous hydrogen ated carbon (a-CHx) overcoats. Temperature-programmed desorption experiment s were performed using 2,2,2-trifluoroethanol (CF3CH2-OH) coadsorbed with w ater and perfluorodiethyl ether [(CF3CF2)(2)O] coadsorbed with water. The r esults indicate that the presence of water increases the desorption energy of CF3CH2OH on the a-CHx overcoat but decreases the desorption energy of (C F3CF2)(2)O on a-OHx overcoats. The implication of these results is that the re is a net increase in the mobility of PFPE lubricant films when exposed t o humid environments.