Roughness of thin perfluoropolyether lubricant films: Influence on disk drive technology

In disk drive technology, lubricant thickness and roughness are important, but often overlooked, contributors to slider-disk spacing. In this paper, w e use X-ray reflectivity to measure the thickness and lubricant-air roughne ss of a perfluoropolyether lubricant (Fomblin Zdol) on silicon wafers and c arbon overcoats. For Zdol on smooth silicon, the roughness increases with i ncreasing lubricant thickness consistent with capillary wave roughening. Fo r Zdol on the rougher surface of amorphous hydrogenated carbon, the,lubrica nt smoothes to a value limited by the capillary wave roughening. We show th at the lubricant density above the surface does not reach the density of ai r until approximately 3 sigma away from the average lubricant thickness. Th is lubricant-air interface width contributes substantially to current and f uture slider-disk spacings.