Novel microstructure and surface conductivity of ultra-thin metallic films on Si(111)

An unusual frequency-dependence of the resistivity for ∼ 2.5 Å of Pd on Si(111) is determined by electron energy loss spectroscopy and analyzed using the Bruggeman effective medium theory. This analysis together with hydrogen titration studies indicate a microstructure having small ({less-than or approximate} 7 A ̊) metallic clusters embedded in the Si surface. We also show that electron tunnelling via surface states gives an important contribution to the d.c. conductivity of such metallic films. © 1985.