ELECTRONIC-STRUCTURE OF SILVER AND COPPER ULTRATHIN FILMS ON V(100) -QUANTUM-WELL STATES

Angular-resolved photoemission and inverse-photoemission spectroscopie s have been used to investigate the valence-electron states in ultrath in films of sliver and copper deposited on a V(100) surface. For both noble metals, discrete s-p derived states are observed within the Delt a(1) gap of the vanadium substrate (approximately +/- 2 eV around E(F) ) These states are analyzed using a simple quantum-well picture. For a pseudomorphically grown (centered tetragonal) silver film in the bulk like limit we have determined k(F) (1.19 Angstrom(-1)) and the energie s of critical points, X(1) (7.60 +/- 0.15 eV) and X(4') (2.5 +/- 0.3 e V) in the E(k) dispersion of the Delta(1) band in the Gamma-Delta-X di rection. The bottom of the Delta(1) band, i.e., Gamma(1) point, was es timated to be -6.4 +/- 0.3 eV by fitting the experimentally determined points with a free-electron parabola. Ln the case of copper overlayer s, it was not possible to determine the dispersion of the bulklike Del ta(1) band because Cu films thicker than two monolayers showed poor or der. At low coverages (1-2 ML) of both silver and copper, we find that dispersion in k(parallel to) of the discrete s-p quantum-well states is described by a significantly enhanced electron effective mass (m>2 m(e)). This is interpreted as due to strong hybridization of these sta tes with the d derived states of the vanadium substrate.