A RESONANT PHOTOEMISSION-STUDY OF THE AL65CU20RU15 ICOSAHEDRAL ALLOY

Measurements with photoemission spectroscopy in the photon-energy range 41-140 eV have been used to determine the valence band of the stable icosahedral Al65Cu20Ru15. An investigation of resonant photoemission near the Ru 4p-->4d transition shows that the feature in the valence band with the maximum intensity at 1.3 eV below the Fermi level is predominantly due to the Ru 4d-derived states. This has been additionally confirmed by measuring the photoemission spectra in the constant-initial-state mode and by employing the effect of the Cooper minimum in the photoionization cross section of the Ru 4d orbitals. The feature in the valence band with the maximum intensity at 3.8 eV below the Fermi level has been identified as being due predominantly to the Cu 3d-derived states. The strong decrease of intensity towards the Fermi level has been interpreted as being indicative of the presence of a pseudo-gap at the Fermi level. It has been indicated, however, that the Fermi cut-off also contributes to the observed intensity decrease. No unusual features in the valence band of icosahedral Al65Cu20Ru15 that could be ascribed to its quasiperiodic nature have been observed within the resolution of the experiment.