High-Resolution Core Level Photoemission of Mg:Ag Deposited on Tris(8-hydroxyquinolato) Aluminum Probed by Synchrotron Radiation

Deposition of magnesium on tris(8-hydroxyquinolato) aluminum (Alq3) precovered with a thin silver dopant was investigated with high-resolution core-level photoemission via synchrotron radiation. First, the noble-metal dopant that make contact with the molecules reside at the vicinity of the pyridyl ring, similar to the case of the alkaline earth metals on Alq3. Further, a fit to this Alq3-derived Ag component delivers a non-zero Doniach-Sunjic singularity index of 0.061, suggesting that the incorporated Ag dopant behaves as a metallic cluster. Upon Mg adsorption on the Ag/Alq3 surface, the size of the Ag cluster remains intact, but its binding energy now appears lower than that of the bulk. The charge added onto the clusters comes from part of Mg which is mixed with Ag. As to the other part of the Mg atoms, they gather about the chelated oxygen. This is certainly in contrast to the case of Mg on Alq3 where Mg accumulates at the vicinity of the nitrogen atoms