Flyability failures due to siloxanes at the head-disk interface revisited

In an earlier report, flyability failures due to siloxanes were investigated comparing disks with either Z-Dol or X-1P lubricant. On the Z-Dol disk, the head-disk interface failed at 47 h (h) and the slider accumulated silicon oxide smears, whereas the X-1P disk did not fail (truncated at 300 h) and the slider remained clean. The contrasting performance was rationalized by an assumed mechanism in which degraded lubricant was essential. In this paper, we demonstrate that siloxanes can be tribochemically converted into silicon oxides without any lubricant on the disk or slider. Lubricant degradation is, therefore, not needed for the formation of silicon oxides from siloxanes. We find that siloxane oligomers on Z-Dol disks form micrometer-sized droplets 100 nm in height, whereas on X-1P disks, siloxanes spread out as a very thin film. The siloxane droplets on Z-Dol disks may lead to flyability failure because they exceed the fly height. The presence or absence of siloxane droplets on disk surfaces may be explained in terms of surface wetting properties characterized by contact angle measurements.