Many-electron effect in the Fe L 3-M 4,5M 4,5 Auger electron spectrum of ultrathin Fe films grown on Cu(1 0 0)

Abstract

D’Addato et al. [S. D’Addato, P. Luches, R. Gotter, L. Floreano, D. Cvetko, A. Morgante, A. Newton, D. Martin, P. Unsworth, P. Weightman, Surf. Rev. Lett. 9 (2002) 709] studied the variation with Fe coverages in the relative Fe L 3-M 4,5M 4,5 Auger electron spectroscopy (AES) spectral satellite intensity of ultrathin Fe films grown on Cu(1 0 0) by sweeping photon excitation energy through the Fe L 2-level ionization threshold. They interpreted that the M 4,5 hole in the L 3M 4,5 double-hole state created by the L 2-L 3M 4,5 Coster–Kronig (CK) decay remains localized for longer than the L 3-hole lifetime for the 0.3 and 10 ML coverages but has a lifetime comparable to the L 3-hole lifetime for the 1 ML coverages. The present many-body theory shows that when the M 4,5 hole created either by the CK decay or by the L 3M 4,5 shakeoff hops away from the ionized atomic site and becomes completely screened out prior to the L 3-hole decay, the Fe L 2-L 3M 4,5-L 3-M 4,5M 4,5 AES main line as well as the Fe L 3 M 4,5 (satellite)-L 3-M 4,5M 4,5 one, both of which are identical in line shape to the Fe L 3-M 4,5M 4,5 one, dominate in the Fe CK preceded AES spectrum. The present analysis shows that the delocalization time of the M 4,5 hole created in the 1 ML Fe/Cu(1 0 0) system by the L 2-L 3M 4,5 CK decay is much shorter than the L 3-hole lifetime so that the Fe L 3-M 4,5M 4,5 AES spectral line shape hardly changes, except for the presence of a very weak spectator L 2-L 3M 4,5-M 4,5M 4,5M 4,5 AES satellite, when the photon excitation energy is swept through the Fe L 2-level ionization threshold. For the 0.3 ML coverages the M 4,5-hole delocalization time is still shorter than the L 3-hole lifetime.