Surface segregation process of dissolved elements on a Fe(1 0 0) surface and the initial oxidation processes of the sulfur segregated surfaces were studied in situ by AES and RHEED. The surface enrichment of sulfur has formed a c(2 x 2) superstructure at elevated temperatures. The Fe(1 0 0)c(2 x 2)-S surface was found to have stabilization effect against initial oxidation. The retardation of oxidation was most enhanced when the sulfur surface concentration reached at the saturation coverage (1/2 ML). The possible physical origins of the stabilization effect are proposed. (C) 2002 Elsevier Science B.V. All rights reserved.