Modification of Shockley states induced by surface reconstruction in epitaxial Ag films on Cu(111)

Epitaxial Ag ultrathin films grown on Cu(111) have been studied by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. In the submonolayer range, the spectroscopic measurements reveal the existence of two parabolic dispersive surface bands associated with the Cu terraces and the Ag islands suggesting the lateral confinement of the electronic states. A thickness dependence of the surface-state energy is evidenced. Moreover, the two well-known atomic reconstructions (moire and triangular superstructures which depend on the preparation temperature) lead to different surface state energies. Photoemission spectra also reflect the transition from the metastable moire structure into the triangular one. These results clearly demonstrate the strong sensitivity of the surface-state energy to the in-plane atomic structure.