Interfacial reactivity in the Co/CuO samples as investigated by x-ray photoelectron spectroscopy

The interfacial reactivity at the Co/CuO interfaces has been investigated in situ by the technique of x-ray photoelectron spectroscopy. Thin films of cobalt were evaporated on the CuO substrates by the technique of e-beam. The depositions were undertaken by maintaining the substrates at ambient temperature. Significant differences have been observed in the Cu 2p core level spectra recorded for these samples and that for pure CuO. The Co 2p core level spectrum also shows differences upon comparison with the spectrum for elemental cobalt. These differences arise from chemical interaction occurring at the Co/CuO interface. The curve fitting technique has been utilized to estimate the relative percentages of the constituents at the interface. The interface width has been determined from the relative percentage of the unoxidized cobalt present in the overlayer. The dependence of the interface width has also been explored as a function of annealing temperature. The interface width is much less for the room temperature deposited sample as compared to that for annealed samples. The spectral data also indicate increase in the diffusion of copper oxide through the cobalt overlayer with increasing temperature.