Micro/nanoscale studies of boundary layers of liquid lubricants for magnetic disks (abstract)

The atomic force/friction force microscope is used to study the micro/nanotribiological properties of perfluoropolyether lubricants. Single-crystal silicon wafers were lubricated with nonpolar (Fomblin Z-15) and polar (Fomblin Z-DOL and Demnum S-100) lubricants. The nanowear tests show that the nonpolar (Z-15) lubricant depleted from the wear track within few cycles whereas polar (Z-DOL) lubricant exhibits excellent nanowear resistance with no degradation. The polar lubricant results in a lower value of microfriction as compared to the nonpolar lubricant and unlubricated silicon sample. The effect of thickness of polar lubricant is studied for the thermally bonded Z-DOL lubricant before and after wash. Unwashed polar lubricant film with unbonded fraction exhibited better resistance to wear than that of washed lubricant film. Thicker films are also more durable. Wear experiments with magnetic disks show that lubricant film on a supersmooth disk is more effective in reduction of friction and wear than a smooth disk. Coefficients of friction on micro- and macroscales are compared. Variation in lubricant film thickness results in variation in the coefficient of friction. Thus, friction force microscopy can be used to measure lubricant uniformity with spatial resolution on the order of tens of nanometers. Finally, adhesive experiments show that bonded film behaves as a soft polymeric solid.