XPS depth profile analysis of non-stoichiometric NiO films

• Published in: Surface and interface analysis Vol. 36; no. 1; pp. 17 - 22
• Main Authors: Oswald, S., Brückner, W.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-01-2004; Wiley
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; depth profiling; Exact sciences and technology; factor analysis; Ni oxide; Physics; XPS; Nickel oxides; Oxygen; Annealing; Factor analysis; Inorganic compounds; Spin systems; Ni oxide; Transition element compounds; Nonstoichiometry; Sputtering; Film growth; depth profiling; Reactive sputtering; XPS; Argon; Depth profiles; X-ray photoelectron spectra
• ISSN: 0142-2421; 1096-9918
• DOI: 10.1002/sia.1640

Antiferromagnetic NiO films used for pinning layers in spin valve systems were prepared by reactive sputtering from an NiO target with variation of the oxygen/argon mixture in the sputter gas. Using XPS depth profiling we investigated the NiOx overstoichiometry (x > 1) in the films that was found by other methods and the chemical changes in the films during annealing. A direct detection of Ni3+ failed because of strong preferential sputtering with the formation of metallic Ni during sputtering. By means of factor analysis a qualitative description of the overstoichiometry is possible. Indirectly it could be shown that metallic Ni is already formed in the oxide layers during annealing. It can be concluded that the stability of the NiOx films decreases with increasing deviation from stoichiometry (x > 1). Copyright © 2004 John Wiley & Sons, Ltd.