AES STUDY OF OXIDATION OF SURFACE AND BULK SULFIDES OF NI

The interaction of oxygen with sulfur-covered nickel and nickel sulfide surfaces was investigated by AES. For the adsorbed sulfur the interaction appears to proceed via an intermediate step prior to the removal of sulfur; a proposed mechanism of interaction is presented. This interaction is dependent on oxygen pressure. Under certain conditions three-layer oxide can form on a buried sulfur layer and this oxide is destabilized by the presence of sulfur. Oxidation of the nickel sulfide appears to be similar to that of the adsorbed-sulfur-on-nickel system with regard to oxide buildup. The effect of temperature on these processes is discussed.