O2 induced Cu surface segregation in Au?Cu alloys studied by angle resolved XPS and DFT modelling

E. VOLKER; F. J. WILLIAMS; E. J. CALVO; T. JACOB; D. J. SCHIFFRIN

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2012 vol. 14 p. 7448 - 7455

1463-9076

Surface segregation effects on polycrystalline Au?Cu alloys (Au0.80Cu0.20, Au0.85Cu0.15 and Au0.90Cu0.10) were studied at room temperature by angle resolved XPS (ARXPS) and density functional theory (DFT) before and after exposure to O2. Au surface enrichment was found as predicted from calculations showing that this process is energetically favourable, with a segregation energy for Au in a Cu matrix of À0.37 eV atomÀ1. Surface enrichment with Cu was observed after exposure to O2 due to its dissociative adsorption, in agreement with DFT calculations that predicted an energy gain of À1.80 eV atomÀ1 for the transfer of Cu atoms to a surface containing adsorbed oxygen atoms, thus leading to an inversion in surface population.