De-wetting of lubricants on hard disks

The de-wetting process of Zdol-type lubricants on hard disks has been studi ed at the molecular scale with scanning polarization force microscopy (SPFM ) and ellipsometry. It was found that de-wetting occurred over hours to day s when the initial lubricant layer was thicker than one monolayer (similar to 20 Angstrom thick). De-wetting was found to take place in a layered fash ion for Zdol-TX and Z-Tetraol, with weakly bound second layers accreting in to droplets, however, no layering was seen for Zdol during de-wetting, only droplets. The droplets eventually grew to the point where they could be ob served by optical microscopy. In all cases, the first monolayer remained bo und to the surface. Although the atomic force microscopy (AFM) tip could ea sily penetrate this first layer, it did not remove it. (C) 2000 American In stitute of Physics. [S0021-9606(00)71306-7].