Determination of lubricant film thickness on a particulate disk surface by atomic force microscopy

The ability of the atomic force microscope (AFM) to measure the lubricant film thickness on the surface of particulate disks is demonstrated, and experimental results are presented. AFM measure the thickness of the lubricant film at a particular location on the disk surface with a lateral resolution of the order of the AFM tip radius, approximately 1000 AA. For an unused disk, 50-70 AA of lubricant thickness is found. After the disk has been in use for several years, the lubricant thickness decreases to 35-55 AA. In both cases, the lubricant is uniformly distributed on the disk surface, although somewhat more uniformly on the used disk. For all types of disks studied, most of the lubricant resides below the disk surface, presumably in the medium's porosity, with only a molecular thin film of lubricant on the surface.>