Thickness periodicity in the Auger line shape from epitaxial (111)Cu films

The 61 eV MMM Cu Auger line doublet was recorded in the derivative mode as a function of thickness for epitaxial (111)Cu films approximately 1500 Å thick. The overlap of the doublet lines makes it possible to define a measure of the doublet profile called the “R -factor” as a ratio of the peak-to-peak heights of the small overlap oscillation to that of the major oscillation. To within the experimental error, it was found that the R -factor varies with a periodicity of approximately one monoatomic layer as the film thickens. Since these films grow by a layer growth mechanism, the surface topography varies periodically with the number of monolayers deposited, going from a smooth to a rough to a smooth, etc. surface. It is believed that the occurrence of such a periodicity implies that there is a difference in the electronic structure at the surface of the flat areas of the film from that at the edges of monolayer high, flat islands. The amplitude of the oscillation in R is interpreted to be a measure of the relative amounts of edge area compared to flat area. These results show that it is possible to use Auger electron spectroscopy to monitor surface topography and the electronic structure changes that accompany the topographical changes occurring when epitaxial films grow by a layer growth mechanism.