Formation of Quasi-Compounds on Metals

Abstract

When clean Ag(110), Cu(110), and Ni(110) surfaces are exposed to O₂, one can observe the growth of one-dimensional strings of (–AgO–) on Ag(110), (–CuO–) on Cu(110), and (–NiO–) on Ni(110) surface, which are evidently not the adsorption of O(a) on these surfaces, but the formation of new materials on these surfaces. The new materials are named “quasi-compounds,” which take own stoichiometry and structure like that of a molecule or compounds. When a p(3 × 1)(–NiO–)/Ni(110) surface is exposed to H₂, H₂ molecules do not react with (–NiO–) strings, but a new quasi-compound of (–NiH–) strings is formed by the reaction of H(a) atoms with Ni atoms. In contrast, when a Cu(100) surface is exposed to O₂, O(a) atoms make minimum-size c(2 × 2)-O domains with adsorbed O(a) atoms instead of the formation of quasi-compound as observed on Cu(110) surface. If a quasi-compound reacts, an additional new quasi-compound is formed. A prominent example is the reaction of Cu atoms with (–AgO–) strings on the Ag(110) surface as will be mentioned in Chap. 5. The formation of (–CuO–).