Frictional properties of perfluoropolyether monolayers investigated with quartz resonators

The high-frequency frictional properties of thin lubricating layers of perf luoropolyethers coated onto the surface of quartz-crystal resonators were p robed by measuring the increase in resonance bandwidth when the quartz surf ace comes into contact with a ceramic sphere. For a lubricant thickness of up to 11 Angstrom, a maximum in bandwidth is observed. The width and the he ight of the maximum decrease with increasing lubricant thickness. This is a ttributed to dissipation occurring during intermittent contact between the substrate and the sphere. With a 25 Angstrom lubricant film the sphere disc ontinuously jumps into contact, after which the movements of the sphere and the quartz are locked. (C) 2001 American Institute of Physics.