Effect of lubricant bonding on nanotribological properties on HDD

Perfluoropolyethers (PFPE) are employed as lubricants at head-disk interface in hard disk drives (HDD) to reduce friction and wear. The interaction between the lubricant layer and the carbon underlayer may be more important to the nanotribological performance of HDDs than the bulk properties of PFPE lubricants. The effect of lubricant thickness and bonding on the tribological behaviour of HDDs is conducted using the hard disk samples coated with Z-DOL with different thickness and bonding. The study involves the chemical analysis by XPS and friction test by AFM/LFM. A commercial hard disk surface is divided into four regions, each of which is treated by different solvent such as acetone and perfluorocarbon to obtain different lubricant thickness and bonding. The friction coefficient between the AFM tip and the disk surface treated by perfluorocarbon is close to that between the AFM tip and the original lubed surface without any treating. On the other hand, the friction coefficient between the AFM tip and the disk surface treated by acetone is much higher compared to that between the AFM tip and the original lubed surface untreated. The results of friction coefficients coincide very well with that of XPS, which demonstrates that acetone has weakened the bonding between the lubricants and carbon underlayers. This indicates that the bonded fraction of lubricant layers plays a main role in lubrication.