Inelastic electron scattering is used to determine the frequency-dependent resistivity of ultrathin metallic films on Si(111). The experimental data are analyzed in the single-scattering regime using dipole scattering theory. An unusual frequency dependence of the resistivity is found for low coverages of Pd on Si(111) and analyzed using the Bruggeman effective-medium theory. This analysis together with hydrogen-titration studies indicates the presence of metallic clusters embedded in the surface. We also show that electron tunneling via surface states gives an important contribution to the dc conductivity of these ultrathin granular metal films on Si(111).

• Received 13 August 1984

DOI:https://doi.org/10.1103/PhysRevB.31.1856