Photoemission studies of zinc-noble metal alloys: Zn–Cu, Zn–Ag, and Zn–Au films on Ru(001)

Abstract

Zn and the noble metals alloy when coadsorbed on Ru(001). The properties of Zn–Cu, Zn–Ag, and Zn–Au alloys have been studied using core- and valence-level photoemission and temperature programmed desorption. Alloy formation induces only small shifts (−0.2 to −0.3 eV) in the position of the Zn 2p, 3s, and 3d levels. In contrast, the core and valence levels of the noble metals show large shifts toward higher binding energy. For small amounts of Cu, Ag, and Au dissolved in Zn multilayers, the shifts in the core levels of the nobel metals follow the sequence: Cu(2p3/2), 0.8 eV≊Ag(3d5/2), 0.8 eV<Au(4f7/2), 1.4 eV. The magnitude of the shift increases as the Pauling electronegativity of the noble metal increases. However, the sign of the shifts for the Cu(2p3/2), Ag(3d5/2), or Au(4f7/2) levels is not directly determined by the direction of charge transfer within the corresponding Zn-noble metal bond.