X-ray and neutron reflectometry study of copper surface reconstruction caused by implantation of high-energy oxygen ions

Combination of neutron and X-ray reflectometry was used to study the vertical structure of 100 nm-thin copper films with implanted oxygen ions of energy E = [10-30] keV and doses D=[0.2-5.4]x$10^{16}$ $cm^{-2}$. The study shows that oxygen ion implantation with an energy of E = 30 keV leads to the formation of a 3 nm thick layer on the surface. Density and copper/oxygen stoichiometry of the observed surface layer are close to $Cu_2O$ oxide. We attribute the $Cu_2O$ oxide formation to highly mobilized copper atoms generated by stimulated ion implantation.