Gan, L.Gomez, R. D.Powell, C. J.McMichael, R. D.Chen, P. J.Egelhoff, W. F. Jr.We have investigated the effectiveness of Al, Au, Cu, Ni, Fe, and Ta films with thicknesses up to 4 nm for protecting a Co surface from oxidation in air at room temperature. The distinct change in the Co 2p3/2 core-level line shape observed by x-ray photoelectron spectroscopy upon the oxidation of Co makes it a simple matter to identify the fractions of the Co that are in the metallic state and in the oxidized state. We find that the best choices for protecting Co from oxidation are Al and Ta. We found that Au, which is one of the most popular choices, is not particularly effective for protecting Co.en-USoxidationoxidation barriersArticle