Photoemission study of Al adlayers on Mn

Al overlayers on Mn, studied by photoemission spectroscopy, show a large lowering of the Al 2$p$ core-level binding energy by 0.5 eV at submonolayer (0.1 ML) coverage. The binding energy increases with coverage and reaches the bulk Al value at $\approx$1.3 ML. The Al 2$p$ core-level spectrum exhibits extra components related to the different chemical environment at the interface, which decrease in intensity with increasing Al coverage. The Al related plasmon loss features appear above 1 ML. The present results are explained by a strong Al $s,p$-Mn 3$d$ hybridization at the submonolayer coverage due to interface alloying, whose influence on the spectra is dominated by metallic bonding in the Al layer as coverage increases. The valence-band spectra demonstrate systematic suppression of Mn 3$d$-like states and emergence of a parabolic free-electron-like Al density of states.

Figure 1

Al 2$p$ core-level spectra as a function of Al coverage on Mn measured with 200 eV photon energy. The spectra have been shifted along the vertical axis for clarity of presentation. The coverage (ML) is indicated for each spectrum.

Figure 2

Al 2$p$ core-level spectra (open circles) recorded with 200 eV photon energy, the fitted spectra (thick solid line), and the DS line-shape components (shaded) obtained from least-squares fitting, for (a–d) different Al coverages on Mn, as indicated, and (e) clean Al(111) surface. Different Al 2$p$ fitting components are marked by $A_1$ (dark gray), $A_2$ (blue), and $A_3$ (green). The extra Gaussian broadening given to the components in (a) is not shown.

Figure 3

Al 2$p$ core-level spectra (open circles) recorded with 105 eV photon energy and the fitted spectra (thick solid line). The DS line-shape components (shaded) obtained from least-squares fitting are shown similar to Fig. 2.

Figure 4

Relative area of peaks $A_1$ (dark gray), $A_2$ (blue), and $A_3$ (green) as a function of Al coverage measured with (a) 200 eV and (b) 105 eV photon energies.

Figure 5

Mn 3$s$ spectra along with the Al related bulk (1${\omega }_p$) and surface (1${\omega }_s$) plasmon features as a function of Al thickness on Mn. The spectra have been recorded with h$\nu =350$ eV. The coverage (ML) is shown for each spectrum.

Figure 6

Valence-band photoemission spectra of Al adlayers on Mn as a function of Al coverage recorded with 200 eV photon energy.