Unoccupied electronic surface states on Cu(110)

Abstract

Using k-resolved inverse photoemission spectroscopy, we have found an unoccupied Shockley-type surface state on the Cu(110) surface and measured its E(k${\to }_{\mathrm{para}}$) dispersion along the Γ¯ X¯ symmetry line. Its minimum energy, $E_F$+(2.0±0.4) eV, is found at the surface Brillouin-zone boundary X¯ in accordance with thin-film calculations of Dempsey, Kleinman, and co-workers. In addition, we interpret a weak emission feature near the vacuum level in the near-normal-incidence spectra of Cu(110) as arising from image-potential surface states.