ELECTRONIC AND CRYSTALLOGRAPHIC STRUCTURES OF 2D SILVER ADLAYERS ON GE(111)

We have studied the formation of the Ag/Ge(111) interface with synchro ton radiation photoelectron spectroscopy. We compare the valence band states and the core-level spectra for room temperature adsorption and for different superstructures. Special attention is paid to the square -root 3 x square-root 3 structure since its STM images are identical t o those of Ag/Si(111), while a structural analysis by surface X-ray di ffraction leads, instead, to a geometry similar to that of Au/Si(111). Our photoemission results support the (rotated) trimer model proposed by the X-ray data.