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

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 $-75\mathrm{meV}$ $(+20\mathrm{meV})$ from experiment and $-71\mathrm{meV}$ $(+20\mathrm{meV})$ from the DFT calculations. For Al(111), the corresponding values are $-27\mathrm{meV}$ $\left(0\mathrm{meV}\right)$ from experiment and $-14\mathrm{meV}$ (−) 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 $\mathrm{Al}2p$ line shape was found to contain structure caused by a sharp no-phonon line and a broad and weak phonon replica.

Figure 1

The variation of the total energy of a seven-layer Al(100) slab with the relaxation $\mathrm{\Delta }{d}_{12}$ of the first interlayer spacing. For each value of $\mathrm{\Delta }{d}_{12}$, an optimization has been performed of the second interlayer spacing $d_{23}$.

Figure 2

The $\mathrm{Al}2p_{3∕2}$ eigenvalue, relative to the Fermi level, at different layers and for different slab thicknesses from LAPW ground-state calculations.

Figure 3

$\mathrm{Al}2p$ spectra from Al(111) measured at the indicated photon energies. Measured at $100\mathrm{K}$ and normal emission.

Figure 4

Bulk sensitive $\mathrm{Al}2p_{3∕2}$ spectrum from Al(111) excited at a photon energy of $82\mathrm{eV}$. A decomposition into bulk (higher binding energy) and surface (lower binding energy) components is included. Each of these components consists of a no-phonon line (black line) and a phonon replica (grey line). The resulting fit is included (black line).

Figure 5

$\mathrm{Al}2p$ spectrum from Al(111) at a photon energy of $90\mathrm{eV}$. A decomposition into surface (lower binding energy) and bulk (higher binding energy) components is included. Each of these components consists of a no-phonon line (black line) and a phonon replica (gray line). The resulting fit is included (black line).

Figure 6

$\mathrm{Al}2p$ spectra from Al(100) measured at the indicated photon energies. Measured at $100\mathrm{K}$ and normal emission.

Figure 7

$\mathrm{Al}2p_{3∕2}$ spectrum from Al(100) at $h\nu =95\mathrm{eV}$. A decomposition into second layer (higher binding energy), bulk (middle binding energy), and two crystal field split surface (lower binding energy) components is included. Each of these components consists of a no-phonon line (black line) and a phonon replica (gray line). The resulting fit is included (black line).