(564e) Surface Chemistry of Carbon Overcoats for Magnetic Data Storage
AIChE Annual Meeting
2006
2006 Annual Meeting
Organic Electronics (Co-sponsored by the Korean Institute of Chemical Engineers)
Surfaces and Interfaces
Thursday, November 16, 2006 - 2:40pm to 3:00pm
The final steps in the production of magnetic hard disks include the deposition of an amorphous carbon film, removal of the disk from the vacuum and the application of the perfluoropolyalkylether (PFPE) lubricant via dip-coating. Removal from vacuum and exposure to ambient air results in the immediate oxidation of the amorphous carbon film. The kinetics of this process are so rapid, however, that they have not been studied carefully. Furthermore, the effect of the oxidation on the bonding of the PFPE lubricant with amorphous carbon film is unknown. Vapor phase lubrication lubricates the amorphous carbon film in situ by absorbing lubricant vapor on carbon film surface without exposing to air. In vapor phase lubrication the amorphous carbon film surface can be oxidized under controlled conditions immediately prior to lubricant adsorption. The oxidation kinetics of hydrogenated amorphous carbon (a-CHx) has been studied using x-ray photoemission spectroscopy (XPS) in an apparatus that allows oxidation of freshly deposited a-CHx films. Although the surfaces of a-CHx films are heterogeneous in nature, the film oxidation kinetics in O2 can be predicted by a Langmuir-Hinshelwood reaction with a relatively low rate constant for oxidation. Temperature programmed desorption (TPD) has been used to study the desorption kinetics and desorption energies of perfluorodiethyl ether ((CF3CF2)2O) and 2,2,2-trifluoroethanol (CF3CH2OH), models for the ether backbones and hydroxyl endgroups of PFPE lubricant, adsorbed on fresh and oxidized a-CHx films. Our measurements clearly reveal, for the first time, the oxidation of the a-CHx surface increases the desorption energy of CF3CH2OH by intensify its hydrogen bonding to the a-CHx surface. Although this effect has been assumed to exist it has not been observed directly or quantified. These results imply that the oxidation of the fresh a-CHx film may be a means to control or tailor the surface properties to optimize the properties of the lubricant-overcoat interface in hard disks.