XPS, UPS, and STM studies of nanostructured CuO films

A Cu1O1.7 oxide film containing a large amout of superstoichiometric oxygen was obtained by low-temperature oxidation of metallic copper in the oxygen plasma. An STM study of the film structure showed that ∼10 nm planar copper oxide nanocrystallites with particles packed parallel to the starting metal surface. In an XPS study, the spectral characteristics of the Cu2p and O1s lines indicated that particles with a CuO lattice formed (Ebnd(Cu2p3/2) = 933.3 eV and a shake-up satellite, Ebnd(O1s) = 529.3 eV). The additional superstoichiometric oxygen is localized at the sites of contact of nanoparticles in the interunit space and is characterized by a state with the binding energy Ebnd(O1s) = 531.2 eV. Due to the formation of a nanostructure in the films during low-temperature plasma oxidation, the resulting copper oxide has a much lower thermal stability than crystalline oxide CuO.