Absolute thickness measurement and surface morphology observation of perfluoro-polyether lubricant for hard disk by SOR X-ray and AFM

摘要

In a hard disk drive, magnetic write/read heads are flying at height about 10nm over the magnetic disk surface with very high speed. Therefore, direct contact between head and disk sometimes occur, and fatal data losses may occur by a head crash. To prevent these irreversible damages on a disk surface, PFPE (perfluoro-poly-ether) liquid lubricant is widely used as protective coating by nano-meter order thickness. Precise measurement of absolute thickness of liquid lubricant is very important issue to understand the roll of lubricant layer. In this study, absolute thicknesses of PFPE lubricant had been measured by using SOR (Synchrotron Orbital Radiation) X-ray reflectivity method directly. Reflective X-ray spectra from disk surfaces were successfully detected in large dynamic range, since X-ray intensity of the Spring8 beam is very high. On the other hand, Interaction between lubricant molecule and DLC (Diamond Like Carbon) surface was also investigated by using SOR-XPS (X-ray Photoemission Spectroscopy) method. Furthermore, surface morphology of PFPE lubricant layer on DLC overcoat was observed by AFM (Atomic Force Microscope) with a specially made probe that has fluoro-coating on its surface for direct observation.