Analytical determination of the surface energy of sub-5nm head-disk interfaces accounting for multilayer effects

Abstract

In this work, a five-layer HDI configuration was employed to derive a simple way to relate the multilayer Hamaker constant to an effective surface energy of the HDI. Specifically, the five layers of the HDI include two layers on the slider [diamondlike carbon (DLC) overcoat, Al2O3–TiC] and two layers on the disk (lubricant, DLC overcoat) as well as the air gap (or flying height). Following the formulation for two equivalent homogeneous surfaces, one can derive the effective surface energy of the five-layer model. To investigate the effect of the topmost layer thicknesses of the slider and disk on the surface energy, they were first varied from 2 to 5nm and from 0.5 to 2nm, respectively. It was found that the surface energy depends largely on the disk lubricant thickness while it has little dependence on the slider DLC thickness. Lubricant pickup by the slider and its effect on the surface energy was also investigated and it was found that the overall surface energy of the interface is lower when there is lubricant pickup.