SURFACE CONDUCTIVITY OF SI(111) 7 X 7 WITH SUBMONOLAYER PB-COVERAGES

The conductivity of Si(111)7 x 7 surfaces is studied in situ during room temperature deposition of submonolayers Pb. The conductance shows an initial decrease to a shallow minimum for coverages between 0.05 and 0.1 monolayer (ML) and a subsequent steep increase between 0.4 and 0.7 ML. Both continuous and intermittent deposition have been applied, to distinguish between equilibrium and transient effects. The results must be interpreted in terms of changes in the nature of surface states that pin the Fermi level and 2D percolation. A relation is suggested to different existing submonolayer structural phases