Ormation and electric properties of disordered Yb layers on Si(111)7x7 surface

Interface formation in Yb/Si(111) system has been investigated by AES and EELS spectroscopy and in situ Hall measurements at room temperature. It was established that interface formation process may be divided into five stages: 1) two-dimensional growth of Yb (up to two monolayers), 2) intermixing and formation of two-dimensional Yb silicide, 3) formation of 3D silicide islands, 4) growth of Yb on 3D silicide islands, 5) coalescence of 3D Yb - Yb silicide islands and formation of continuos Yb film. We attribute the observed conductivity character in Yb/Si(l 11) system to the evolution of morphological and electrical properties of the growing Yb layer (21) Yb, silicide, metal) rather than to the changes within the space charge layer under the surface. Two-layer calculations have shown that holes are majority carriers in the deposited Yb layer within all the coverage range studied. Some amplitude oscillations have been observed in sheet conductivity, hole mobility and surface hole concentration within the coverage range below 6 ML where formation of a continuos Yb silicide film completes. Conductivity oscillations are explained by transition from semiconductor-type conductivity at the first Growth stages (two-dimensional Yb growth) to metal-like conductivity of 2D and 3D Yb silicide films. It was shown that thin continuos Yb film (13) MI) has the resistivity (16 muOmega(.)cm) close to the bulk refractory metals.