Experimental and theoretical surface core-level shifts of aluminum (100) and (111)

Abstract

The surface core-level shifts of Al(111) and Al(100) have been measured using high-resolution core-level photoemission spectroscopy and calculated using density functional theory (DFT). For Al(100), the $2p$ core-level shift of the first (second) layer was determined to be $\ensuremath{-}75\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ $(+20\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$ from experiment and $\ensuremath{-}71\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ $(+20\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$ from the DFT calculations. For Al(111), the corresponding values are $\ensuremath{-}27\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ $(0\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$ from experiment and $\ensuremath{-}14\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ (\ensuremath{-}) from the DFT calculations. Core-level splittings caused by the low-symmetry crystal fields at the (111) and (100) surfaces have also been studied. These splittings turn out to be much smaller than previously reported provided proper care is taken of the influence of the core hole screening and of core--valence exchange beyond the DFT level. Finally, the experimental $\mathrm{Al}\phantom{\rule{0.3em}{0ex}}2p$ line shape was found to contain structure caused by a sharp no-phonon line and a broad and weak phonon replica.