XPS and x-ray diffraction characterization of thin Co-Al-N alloy films prepared by reactive sputtering deposition

Thin (Co0.8Al0.2)(100-x)N-x (x = 0-30 at.%) alloy films prepared by a reactive radio frequency (r.f.) sputtering method were characterized by XPS and x-ray diffraction (XRD), The film with no nitrogen consisted of a CsCl-type CoAl metallic compound, while the nitrogen-containing alloys were composed of very fine AIN and face-centered cubic (fcc) Co phases. The quantitative XPS analysis under an assumption of uniform distribution of all the elements resulted in much lower concentrations of Co and higher concentrations of Al and N in comparison with the bulk composition for the nitrogen-containing alloys. By taking account of the granular structure of the alloy films, i.e. the nanoscale particles of fee Co embedded in the AIN compound, the results of quantitative XPS analysis were explained successfully. Moreover, the thickness of the AIN layer and the size of the fee Co particles were also able to be estimated under the nanoscale structure models. The results were in good agreement with observation by transmission electron microscopy, especially when a nanostructure model was adopted where nanoscale Co-N particles are dispersed in AlN matrix in a simple cubic-like arrangement. (C) 1998 John Wiley & Sons, Ltd.