Epitaxial Formation of Adsorbed Multilayers as Studied by ESDIAD: NH3 Adsorption on Top of Chemisorbed CO on Nickel Crystal Surfaces

摘要

The epitaxial growth of an adsorbed layer of NH3 on top of chemisorbed CO on Ni(111) and Ni(110) surfaces was studied using ESDIAD. A strong interaction yielding an activation energy for NH3 desorption of 12 kcal/mol was observed. This interaction, possibly involving hydrogen bonding, between the adsorbed NH3 and adsorbed CO causes a tilting of the NH3 molecules on the CO-covered Ni surfaces. For the NH3/CO/Ni(110) system, the two-fold symmetry of the underlying Ni substate is transmitted through the CO spacer layer to the NH3 overlayer. This symmetry transfer was not observed for the NH3/CO/Ni(111) system at the current resolution of our ESDIAD detection system.