The dispersion of valence electrons in the perpendicular direction of (111)-oriented Li films formed by evaporation of the alkali metal onto Cu(111) is studied by photoemission $(h\nu =4.5\mathrm{}–26\mathrm{eV}).\mathrm{}$ The conventional bulk band mapping method fails at low photon energies when interband transitions are expected from states near below $E_F.$ In this energy range the dispersion is instead determined from the energies measured for discrete quantum-well-like overlayer states resolved for 1–17 atomic layers thick Li films. For films thick enough (>30 ML) for saturation of the shape of photoemission spectra, the maximum separation between the Fermi edge and the interband emission peak is 2.8 eV. This is an apparent photoemission band width which, according to our estimate is 0–0.4 eV smaller than the actual band width. The quantum well state energies measured for ultrathin films indicate that the Fermi surface is closed with the zone boundary edge 0.1–0.2 eV above the Fermi level.

• Received 28 December 1998

DOI:https://doi.org/10.1103/PhysRevB.60.5217