Formation of a hybrid surface of carbide and graphite layers on Ni(100) but no hybrid surface on Ni(111)

Abstract

Carbide and/or graphite layers were prepared on Ni(100) and Ni(111) surfaces by performing a disproportionation reaction of CO: 2CO→C+CO 2, and by segregation of carbon. It was found that a hybrid surface composed of carbide and graphite layers was built on the Ni(100) surface at temperatures higher than 630 K, but no hybrid carbide and graphite layers were settled on the Ni(111) surface. These results are well explained by comparing the growth temperature of the graphite layer with the decomposition temperature of carbide on Ni(100) and Ni(111) surfaces. The growth temperature of graphite was almost equal on Ni(100) and Ni(111) surfaces, being 630-640 K, The decomposition temperature of carbide is quite different on the Ni(111) surface and the Ni(100) surface. On the Ni(111) surface carbide decomposes at 660 K but the hybrid surface of carbide layers on Ni(100) was stable even at 750 K. A single domain carbide layer was accidentally obtained on a Ni(111) surface so that we succeeded to solve completely the complex carbide pattern on the Ni(111) surface and this is represented by a notation of 1 2γ + 3 γ ,1 1− 3 2γ 2 .This notation becomes exactly equal to the McCarroll's notation of (√39x√39)R16.1°, when γ=5√3/9. The graphite layer on the Ni(111) surface dissolved into the bulk of Ni by making surface carbide at temperatures higher than 870 K.