Occupied and unoccupied band structure of Ag(100) determined by photoemission from Ag quantum wells and bulk samples

Angle-resolved photoemission spectra taken from atomically uniform films of Ag on Fe(100) show layer-resolved quantum-well peaks. The measured peak po sitions as a function of film thickness permit a unique determination of th e initial band dispersion via the Bohr-Sommerfeld quantization rule. This i nformation, combined with normal-emission data taken from a single crystal Ag(100), leads to a unique determination of the final band dispersion. In t his study, we employ a two-band model with four adjustable parameters for a simultaneous fit to these experimental results. The initial and final band dispersions deduced from the fit are accurate to better than 0.03 eV at an y wave vector k within the range of measurement. The analytic formula for t he band dispersions and the parameters for the best fit are given for futur e reference. The Fermi wave vector along [100], normalized to the Brillouin -zone size, is determined to be k(F) /k(Gamma X) = 0.828+/-0.001, which is more accurate than the de Haas-van Alphen result. The corresponding Fermi v elocity is v(F)=1.06 in units of the free-electron value. The combined refl ection phase for the electron wave at the two boundaries is also deduced an d compared with a semiempirical formula. This comparison allows us to deduc e the edges of the hybridization gap in the Fe substrate.