Measurement of disjoining pressure of Z-type perfluoropolyether lubricants on Si and SiNx surfaces

An AFM based measurement of the disjoining pressure (Π) is described. For the measurement of nano-thin fluids on hard substrates it was shown that specific experimental requirements are placed on the cantilever stiffness and probe radius. The disjoining pressure of Fomblin Z03 was then measured on a Si surface and found to be consistent with literature values. The disjoining pressures (Π) of 25 Å Zdol on SiNx films deposited under a flowing-gas of N2 was measured and a sharp decrease in Π was observed with increasing N2 concentration (in the gas) that was assigned to the decrease in the polarizability and/or the density of polarizable species in the surface.