"Quantum-well states in ultrathin Ag(111) films deposited onto H-passivated Si(111)-(1x1) surfaces"
A. Arranz, J.F. Sánchez-Royo, J. Avila, V. Pérez-Dieste, P. Dumas, and M. C. Asensio
Physical Review B 65, 195410 (2002)

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Ag(111) films were deposited at room temperature onto H-passivated Si(111)-(1x1) substrates, and subsequently annealed at 300 °C. An abrupt nonreactive Ag/Si interface is formed, and very uniform nonstrained Ag(111) films of 6-12 ML have been grown. Angle-resolved photoemission spectroscopy was used to study the valence band electronic properties of these films. Well-defined Ag sp quantum-well states (QWS’s) have been observed at discrete energies between 0.5-2 eV below the Fermi level, and their dispersions have been measured along the GK, GM(M'), and GL symmetry directions. QWS’s show a parabolic bidimensional dispersion, with in-plane effective mass of (0.38-0.50)m_o, along the GK and GM(M') directions, whereas no dispersion has been found along the GL direction, indicating the low-dimensional electronic character of these states. The binding energy dependence of the QWS as a function of the Ag film thickness has been analyzed in the framework of the phase accumulation model. A good agreement between experimental data and the above-mentioned model is obtained for the Ag/H/Si(111)-(1x1) system. Hydrogen at the interface not only enhances the Ag film uniformity, but also acts as a barrier modifying the phase change of the Ag-sp electron wave upon reflection at the Ag/Si interface.