Abstract
To protect the interface against intermittent head-disk contact in hard disk drives,nanometer-thick perfluoropolyether(PFPE) films consisting of both "bonded" and "mobile" molecules are applied on the disk surfaces.Molecules retained by the disk after a solvent rinse is defined to be "bonded",while those removed from the disk is defined to be "mobile".Because of their different adsorption states and mobility,the bonded and mobile molecules are supposed to contribute differently to friction properties,which directly impact the stability of ultra-low flying head-disk interfaces.Here by measuring the friction force at light loads and high speeds as a function of bonded and mobile film thicknesses,we studied the contributions of bonded and mobile molecules to the dynamic friction of nanomer-thick PFPE films.We found that mobile lubricant molecules generally tend to decrease friction while bonded lubricant molecules determine the speed dependence of friction.
