Al–Pt intermetallic compounds: HAXPES study

Abstract

Intermetallic compounds in the Al–Pt system were systematically studied via hard X-ray photoelectron spectroscopy, focusing on the positions of Pt 4f and Al 2s core levels and valence band features. On one hand, with increasing Al content, the Pt 4f core levels shift towards higher binding energies (BE), revealing the influence of the atomic interactions (chemical bonding) on the electronic state of Pt. On the other hand, the charge transfer from Al to Pt increases with increasing Al content in Al–Pt compounds. These two facts cannot be combined using the standard “chemical shift” approach. Computational analysis reveals that higher negative effective charges of Pt atoms are accompanied by reduced occupancy of Pt 5d orbitals, leading to the limited availability of these electrons for the screening of the 4f core hole and this in turn explains the experimentally observed shift of 4f core levels to higher BE.