Elsevier

Thin Solid Films

Volume 153, Issues 1–3, 26 October 1987, Pages 341-347
Thin Solid Films

An electron spectroscopy study of the growth and thermally activated diffusion of nickel thin films on Al(111) and Al2O3/Al(111)

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Abstract

High-resolution electron energy loss spectroscopy (EELS) and Auger electron spectroscopy have been used to study the interaction of nickel with clean and oxidized Al(111) surfaces. At about 200 K, nickel deposition on Al2O3 forms three- dimensional nickel clusters. The nickel clusters are bonded directly to surface Al-O moieties as determined from the preferential influence of nickel on the Al2O3 surface phonon modes.

Two thermally induced processes compete for dominance for nickel thin films on Al2O3. Heating between 200 and 450 K results in conversion of the nickel clusters to a smoother nickel layer, whereas heating to higher temperatures (450–700 K) causes substantial inward diffusion of the nickel overlayer through defects in the Al2O3 thin film. Only one process occurs for nickel on clean Al(111), as the nickel overlayer simply diffuses steadily into the aluminum throughout the temperature range of about 300–700 K. The Al2O3 layer acts as a barrier to inward diffusion for nickel on Al2O3/Al(111), since the temperature at which inward diffusion starts increases with the thickness of the Al2O3 layer. For nickel deposited onto both clean Al(111) and Al2O3, we find that the metallic aluminum present provides a major driving force for inward diffusion from the nickel overlayer, resulting in Ni-Al alloy formation and segregation of aluminum toward the surface. Our study demonstrates the utility of EELS as a new tool for investigating solid-solid interfaces and thin film barriers.

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Cited by (3)

Paper presented at the 14th International Conference on Metallurgical Coatings, San Diego, CA, U.S.A., March 23–27, 1987.

Permanent address: Department of Chemistry, B-014, University of California, San Diego, La Jolla, CA 92093, U.S.A.

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