Measurement of perfluoropolyether lubricant thickness on a magnetic disk surface

This letter reports on the detection of nanometer-scale perfluoropolyether (PFPE) lubricants with thickness between 2-40 nm on a magnetic disk surface using a nonvibrating Kelvin probe. Magnetic disks were partially dipped in a PFPE lubricant to create lubricated and nonlubricated regions on the dis k surface. The nonvibrating Kelvin probe measures an electrical signal prop ortional to the surface charge gradient at the interfaces between the lubri cated and nonlubricated regions, and is linearly related to the scanning ve locity. The surface charge is related to the difference in surface potentia ls between the lubricated and nonlubricated regions. The surface potential at the nonlubricated/lubricated transition ranges from 7-30 mV. The surface potential is found to be related to the corresponding lubricant thickness through an exponential relationship. (C) 2001 American Institute of Physics .