Surface conduction at phase transitions in (Au,Ag)/Si(1 1 1) submonolayer films

Surface structure and electrical conductance of the (Au,Ag)/Si(1 1 1) two-dimensional system have been studied in situ with low-energy electron diffraction, scanning tunneling microscopy and four-point probe technique. The new surface structure identified as Si(1 1 1)√93 × √93-(Au,Ag) has been found to form upon deposition of ∼0.1 ML of Ag onto Si(1 1 1)α-√3 × √3-Au surface held at 350 °C. With further Ag deposition at this growth temperature, the surface structure evolves to Si(1 1 1)2√3 × 2√3 and eventually to Si(1 1 1)√21 × √21. Structural transformations have been found to be accompanied by non-monotonous changeover of the surface conductance. Possible factors affecting the surface conductivity are discussed.