Angle-resolved photoemission studies of the (Gamma)over-bar Shockley surface state on ordered Cu(111) overlayers on TiO2(110)

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 [TiO2(110)]. The Cu-film thickness was about 17 Angstrom. The Cu(111) <(Gamma)over bar> Shockley state exhibits a noncircular E versus k(parallel to) dispersion around <(Gamma)over bar> 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(parallel to) asymmetry of the state to the nature of the overlayer growth which is only commensurate with the substrate along the <(Gamma)over bar>(M) over bar Brillouin zone direction.