PREPARATION AND OXIDATION OF NI(111)-FE SURFACE ALLOYS

The preparation of Ni(111)-Fe single-crystal surfaces by decomposition of iron carbonyl is described. After decomposition of iron carbonyl on Ni(111), the surface contains except for iron always some carbon and oxygen. Both carbon and oxygen can be removed by an oxidation and reduction cycle. A surface with less than 60% Fe has the hexagonal structure of Ni(111), above 60% Fe a different structure is formed. Interaction with oxygen monitored by AES and ellipsometry is used to assess the chemical properties of Ni(111)-Fe surfaces. There is a consecutive oxidation of first iron and then nickel. The iron oxide formed inhibits the oxidation of underlying Ni, the oxygen uptake thus decreases linearly with the amount of Fe. During oxidation Fe segregates to the surface; at higher temperatures segregation of Fe is more extensive.