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Electronic structure of silver and copper ultrathin films on V(100) - Quantum-well states

Angular-resolved photoemission and inverse-photoemission spectroscopies have been used to investigate the valence electron states in ultrathin films of sliver and copper deposited on a V(100) surface. For both noble metals, discrete s-p derived states are observed within the Delta(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 bulklike limit we have determined k(F) (1.19 Angstrom(-1)) and the energies of critical points, X(1) (7.60 +/- 0.15 eV) and X(4") (2.5 +/- 0.3 eV) in the E(k) dispersion of the Delta(1) band in the Gamma-Delta-X direction. The bottom of the Delta(1) band, i.e., Gamma(1) point, was estimated to be -6.4 +/- 0.3 eV by fitting the experimentally determined points with a free-electron parabola. Ln the case of copper overlayers, it was not possible to determine the dispersion of the bulklike Delta(1) band because Cu films thicker than two monolayers showed poor order. 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*>2m(e)). This is interpreted as due to strong hybridization of these states with the d derived states of the vanadium substrate.

Surface-states; inverse photoemission; band-structure; V(100)

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