Angle-resolved X-ray photoelectron spectroscopic study of the interface chemistry between ultra-thin a-C overcoat and the magnetic layer on magnetic thin film disks

Ultra-thin amorphous carbon (a-C) overcoats of different thicknesses were s puttered on magnetic thin-film disks. The chemistry at the interface of the carbon overcoat and the magnetic layer was studied using Angle-Resolved X- ray Photoelectron Spectroscopy (ARXPS). For a-C overcoats thinner than 20 A ngstrom, the interface was found to consist of metal carbides, metal oxides , and carbon-metal-oxygen complexes, most likely carbonyls. In marked contr ast, a clean transition from metals to carbon with thin metal carbides at t he interface was found for the 40 Angstrom a-C overcoat. The evolution of t he C Is, Co 2p, Ta 4f, and O Is spectra as a function of carbon thickness a nd polar angle suggests that the carbon films form in a layer-by-layer fash ion. The oxygen from the ambient can diffuse through carbon films when the carbon thickness is less than or equal to 20 Angstrom, and leads to the for mation of metal oxides and carbonyls at the carbon-metal interface. Overlay er thickness of similar to 40 Angstrom effectively inhibits oxygen diffusio n and thus leaves the magnetic layer fully intact. This similar to 40 Angst rom carbon thickness points to a required minimum coverage necessary to mai ntain a functionally viable magnetic hard disk as well as other systems tha t use carbon overcoats on polished metal substrates. (C) 1999 Elsevier Scie nce B.V. All rights reserved.