Abstract
We have studied the formation of the Cu/MgO interface with Auger electron spectroscopy and high‐resolution electron energy‐loss spectroscopy (HREELS). Copper overlayers ranging in thickness from 1 to 20 Å were formed on an MgO single‐ crystal substrate by evaporation from a Knudsen effusion cell. Direct Auger spectra for the O KLL, Cu LMM and Mg KLL lines were collected. The evolution of the Auger peak intensities shows that the copper initially forms a complete monolayer, followed by island formation (i.e. Stransky–Krastanov growth). Low energy electron diffraction patterns recorded after Cu deposition confirmed the ordering of the first monolayer.
A significant decrease in energy of the surface MgO phonon peak was observed by HREELS following deposition of 20 Å of copper. Simultaneously with this shift of the phonon energy, we observed a decrease of the intensity ratio of the phonon‐loss and elastic peaks. These results have been interpreted using the dielectric theory. Theoretical spectra of MgO covered by a layer of Cu~2~O obtained by using dielectric constants taken from the literature were able to reproduce qualitatively the decreases in energy and intensity of the phonon‐loss peak with increasing copper thickness.