CARBON, NITROGEN, AND SULFUR ON NI(111) - FORMATION OF COMPLEX STRUCTURES AND CONSEQUENCES FOR MOLECULAR DECOMPOSITION

The decomposition of simple amines on Ni(III) produces a c(5 square-root 3 x 9)rect LEED pattern similar to the one reported earlier after reaction of H2S, C2H4, CO, NO and CH3CN on a Ni(111) surface. We have measured LEED IV curves of the structure obtained after deposition of carbon and nitrogen on a Ni(111) surface. The similarity between these IV curves shows that carbon and nitrogen have similar local geometries. The most intense spots of the c(5 square-root 3 x 9)rect LEED pattern are explained by the formation of a (100) orientation nickel monolayer, with the carbon or nitrogen atoms in the 4-fold hollow sites. This is supported by the qualitative similarity of the IV curves with those of the Ni(100)-(2 x 2)-2C structure. We have also produced a (2 x 6) nitrogen induced structure on Ni(111) and compared it to the very similar (5 square-root 3 x 2)rect structure obtained by adsorption of sulfur on Ni(111) that has also been interpreted as due to a (100) reconstruction of the Ni(111) crystal surface.