Electronic structure of aluminum and aluminum-noble-metal alloys studied by soft-x-ray and x-ray photoelectron spectroscopies

X-ray photoelectron spectra (XPS) and Al K and Al L2,3 soft-x-ray spectra (SXS) of valence bands for aluminum-noble-metal alloys are rationalized on the basis that SXS spectra are dominated by dipole selection rules while XPS spectra chiefly reflect the noble-metal d bands. We find, in agreement with theory, that the main peaks in the Al 3s partial densities of states are at higher binding energy than those for the noble metal d states. Peaks in the Al 3p partial densities of states approximately coincide with the higher-energy peaks in the partial densities of noble-metal d states. The remarkable large chemical shifts of core levels in these alloys are noted and the Au N6,7 SXS emission from aluminum-noble-metal alloys also discussed. The Auger spectra from Al-Ag and Al-Cu alloys provide strong additional evidence that single-atom effects dominate in the Auger processes for these alloys.