Properties of carbon overcoats and perfluoro-polyether lubricants in hard disk drives

The interaction of lubricant with the carbon overcoats of magnetic hard disks was studied experimentally and analytically. The spreading behavior of lubricants on a disk was investigated and a theoretical model for the final film thickness of molecularly thin films was developed using volume conservation and principle of minimum energy. The adhesion and friction of surfaces separated by a molecularly-thin liquid film was studied and the relationship between friction and surface energy of lubricated surfaces was investigated. The experimental results indicate that the adhesive and frictional forces between macroscopic bodies separated by molecularly-thin liquid films are linearly proportional to the excess surface energy of the film. An AFM calibration method for a direct measurement of surface energy on nanostructures covered with molecularly thin liquid films is proposed using the relationship between surface energy and adhesion. Surface energy measurements on the nano- structure of discrete track recording media were performed. Differences in surface energy between the groove and land area were found and explained by changes in carbon overcoat and lubricant film thickness