Sub-monolayer phosphorus coverage measurements on CrCoTaNiP hard disks using PIXE

Abstract The absolute concentration of P in a cyclic phosphazene used as a lubricant additive for hard disk surfaces has been determined by measuring the 4 He + -ion induced K X-ray yield. A new method utilized the detection of X-rays emitted at grazing angles with respect to the sample surface in order to differentiate between those P K X-rays originating from the additive at the surface and those from the hard disk NiP substrate. Under these conditions, P K X-rays emanating from the substrate were totally self-absorbed in the sample. A saturated coverage of 2 × 10 14 atoms/cm 2 was measured for the surface film, with a minimum detection limit estimated to be 5 × 10 13 atoms/cm 2 . Results for a variety of phosphazene concentrations yielded reasonable agreement with relative values measured by X-ray photoelectron spectroscopy.