Electronic structure of quasicrystals deduced from Auger and x-ray photoelectron spectroscopies

Specific features in the electronic structure of Al-transition metal quasicrystals are analysed by a combination of Auger and x-ray photoelectron spectroscopies. We first demonstrate that different degrees of asymmetry in the transition metals' 2p core-level lineshape observed across different types of surface structure correspond to variations in the density of states at the Fermi level, DOS(E-F). Using this effect, we explore the controversial issue of whether the quasicrystalline, decagonal AlNiCo system is electronically stabilized. We find strong evidence for the presence of a reduced DOS(EF) in this system, as expected for electronically stabilized compounds, and as observed in the quasicrystalline, icosahedral AlPdMn and AlCuFe alloys. Finally, qualitative information on the nature of the electronic states in quasiperiodic structures extracted from the core-valence-valence Auger lines are presented and discussed.