Angle-resolved photoemission studies of the [formula omitted]gG Shockley surface state on ordered Cu(111) overlayers on TiO 2(110)

Abstract

Angle-resolved photoemission spectroscopy at hv = 70 eV has been used to investigate the surface electronic structure of a thin metal overlayer [Cu(111)] on an oxide substrate [TiO 2(110)]. The Cu-film thickness was about 17 Å. The Cu(111) \\ ̄ gG Shockley state exhibits a noncircular E versus k ‖ dispersion around \\ ̄ gG in contrast to the behaviour of the single crystal Cu(111) surface state. In addition the overlayer surface state is broadened and shifted by 0.05 eV to lower BE. The energy shift is interpreted as an effect of the surface step density whilst we tentatively assign the k ‖ asymmetry of the state to the nature of the overlayer growth which is only commensurate with the substrate along the \\ ̄ gGM̄ Brillouin zone direction.