Tribochemistry in contact recording

Even though the flying height is approaching molecular dimensions, it is ex pected to decrease as the areal recording density is increased. This study employs a new low-velocity test to obtain ultralow flying height with susta ined intermittent asperity contacts and random seek accessing in a region n ear the middle diameter of the disk. Sensitive surface analytical tools are employed to follow tribochemical changes. Profiles are periodically measur ed across the disk surface using Fourier transform infrared spectroscopy fo r lubricant thickness and scanning-imaging micro-ellipsometry. Zdol lubrica nt is removed from the tested region through evaporation of low molecular w eight scission fragments. The removal rate increased with increasing chemis orbed fraction and decreasing relative humidity. The increased removal rate is attributed to increases in the Zdol relaxation time. A longer relaxatio n time allows more time for bond dissociation following asperity contacts. Chemisorption sites in the tested region were occupied by chemisorbed sciss ion fragments with a carboxylic acid end group. Amine and sodium salts of t he carboxylic acid were detected on the tested regions of Zdol lubricated, and unlubricated, overcoats. The presence of tribochemically generated carb oxylic acid groups on Zdol and overcoat carbon explain the increased water adsorption measured on the tested regions.