Oxygen chemisorption-induced surface phase transitions on Cu(110)

From an interplay between variable temperature scanning tunneling microscopy and density–functional theory calculations, the evolution of oxygen chemisorption-induced surface reconstructions of the Cu(110) surface is determined. The surface reconstructions proceed via a sequential pathway with increasing oxygen surface coverage. The (2 × 1) reconstruction occurs first and then transits to the c(6 × 2) phase with a higher oxygen coverage through a mechanism that consumes the existing (2 × 1) phase with the supply of Cu adatoms from step edges and terraces. The temperature dependence of the (2 × 1) → c(6 × 2) transition demonstrates that the surface phase transition is an activated process for breaking up added Cu–O–Cu rows in the (2 × 1) structure. Comparison between the experimental observations and the theoretical surface phase diagram obtained from first-principles thermodynamic calculations reveals that the (2 × 1) → c(6 × 2) transition takes place at the oxygen chemical potentials that are far above the chemical potential for Cu2O bulk oxide formation, reflecting the existence of kinetic limitations to the surface phase transition and the bulk oxide formation.