Study of chemisorption on copper low-index and stepped surfaces

Adsorption of CHCl₃, O₂, and hydrocarbons has been studied on Cu(111) and stepped surfaces using LEED, AES, and UPS at room temperature. We find that ordered Cl overlayers form upon Cu(111), Cu3(111) × (100)], and Cu5(111) × (100)] surfaces upon exposure to CHCl₃. Exposure to O₂ results in rearrangement of the Cu5(111) × (100)] surface to hill-and-valley regions with large (111) areas, whereas Cu2(111) × (100)] is stable for the same exposure. The photoemission spectra show new energy levels due to C1 above and below the Cu d band region and a small splitting of the halogen p orbitals. Effects consistent with interaction with the Cu d band are observed. Similar effects are observed with oxygen adsorption. The initial rate of Cl or O₂ chemisorption as measured by photoemission is proportional to the density of steps on these surfaces. Apparently, structural effects play an important role in chemisorption on metals (such as copper) with low density of states at the Fermi energy.