Visualization of surface electronic structure: Dispersion of surface states of Ag(110)

Scanning tunneling spectroscopy is used to examine unoccupied surface states of Ag(110). We demonstrate how Fourier transformation of conductance data can be used to determine dispersion throughout the entire surface Brillouin zone, at energies up to the vacuum level. Considerable improvement of previous inverse photoemission data is obtained. Additional features in the Fourier transformed images are found accompanying those states lying in the proximity the Brillouin zone boundary. Their origin is related to the coherent interference of surface state-derived Bloch waves induced by the non-negligible crystal potential, as we determine on the basis of model calculations.