Angle-resolved ESCA methods: Distribution and molecular conformation of perfluoropolyether lubricant

Simple but useful methods for interpreting angle-resolved ESCA data from real-world samples are presented. First is a two-tiered overlayer model allowing thinly covered and thickly covered substrate. It can be productively applied, even in a manual fashion, with common office spreadsheets. Next is a triangle-wave roughness model that can reasonably approximate substrate polishing texture. Finally, a two-slab overlayer model is presented. With the help of canned minimization routines, it can bring out conformation subtleties in overlayer structures and even isolate a deeply buried monatomic layer. The following are presented as examples. Perfluoropolyether (Zdol) lubricant on hard disk carbon overcoat shows coexisting monolayer and multilayer regions consistent with structures identified by surface energy and ellipsometric surface diffusion measurements. Polishing texture of disks is detected but leads to little change in the two-tiered model results. Layering within the lubricant shows significant perfluoropolyether backbone adjacent to the overcoat surface accompanied by a discernible excess of ether oxygen. The latter indicates that the inverted-U conformation sometimes sketched for bonded lubricants is an exaggeration, certainly for the system studied.