Molecular Tribology of Disk Drives

Increasing the amount of information that can be stored in a thin magnetic film in hard disk drives requires that, in the near future, the recording head be brought within 20 nm of the magnetic film while moving at speed in excess of 10 m/s. With such high shear rates and with only room for a few atomic and molecular layers of protecting material, it is essential to obtain a good understanding of the molecular origins of tribological phenomena occurring in a disk drive. This paper examines the tribology of disk drives with an emphasis on how lubrication affects the tribological performance at the molecular level. The topic covered include: 1) how capillary and disjoining pressures determine the distribution of lubricants and meniscus forces at the contacting interfaces; 2) how lubricants and asorbed water vapor affect adhesive forces and friction coeffecients; 3) the interaction and mobility of lubricant molecules on disk surfaces; and 4) the stability and degradation of lubricants during the sliding process.