INTERACTION BETWEEN SULFUR AND OXYGEN ON FE(111)

The sulphur segregation and the influence of the adsorbed oxygen on the bonding states were investigated by means of AES, XPS and LEED methods. The iron surface, initially covered with sulphur, was exposed to an oxygen atmosphere. Adsorbed oxygen displaced sulphur from the iron-sulphur bond, sulphur atoms moved into lower but still near-surface layers, and Fe{single bond}O or O{single bond}Fe{single bond}O and S× clusters were formed. At low sulphur coverages, the metal-sulphur interaction prevailed. The higher the sulphur atom concentration on the iron surface, the shorter was the distance between its atoms, so allowing the formation of a chemical bond between them. By heating up to 720 K, the oxides were decomposed.†Akademie der Wissenschaften der DDR, Otto-Nuschke-Straße 22/23, Berlin, DDR-1086, GDR. © 1990 Pergamon Press plc.