Changes in the local surface geometry with conserved adsorbate coverage and long-range order caused by annealing

Abstract
The ordered c(2×2) Na on Al(100) and (√3 × √3 ) R30° K on Al(111) structures formed at either 100 K or at room temperature are studied by high-resolution core-level spectroscopy. For both systems equal alkali coverages are found at these two temperatures. The core-level spectra, however, show strong changes with temperature. This behavior leads to the surprising conclusion that annealing at room temperature causes an irreversible change in the local geometry, i.e., of the adsorption site, of the overlayer even though neither the long-range order nor the adsorbate coverage changes.