Surface state confinement in a lateral quantum well: The striped Cu(110)(2x1)O surface

We report the response of the well-known Shockley-type surface state, which resides around (Y) over bar on the Cu(110) surface, to the presence of a lateral one-dimensional (1D) superlattice. This grating consists of alternating stripes of reconstructed Cu(110)(2x1)O and unreconstructed Cu(110) and can be prepared by oxygen dosing over a wide range of stripe widths and distances, respectively. Using high-resolution angle-dependent photoemission at room temperature, we study the variation of binding energy, effective mass, linewidth and energy splitting induced by the confinement perpendicular to the (2x1)O stripes. We demonstrate that the surface state electrons on the striped Cu-O surface show confinement properties and photoemission spectra in almost complete analogy to the (Gamma) over bar -surface state electrons on stepped Cu(111) and Au(111) surface [Mugarza , Phys. Rev. Lett. 87, 107601 (2002)]. At low oxygen coverages our data differ from those of an earlier photoemission study of the same system performed with the sample at 100 K [Bertel and Lehmann, Phys. Rev. Lett. 80, 1497 (1998)], which reports the observation of singularities in the density of states of quasi-1D subbands. However, the two studies agree within experimental error limits for the higher oxygen coverages. We explain the apparent difference by the temperature-induced transition from coherent emission out of 2D superlattice bands to incoherent emission from decoupled 1D quantum well states.