Temperature-induced metal–insulator transition on a triangular binary system: Sn/Si(111)

WereportthatametallicSn/Si(111)- × R30° surface undergoes a metal–semiconductor transition upon annealing the surface above the transition temperature of 760 °C. The unique loss peak initially observed weakly from the metallic surfaces in our high-resolution electron-energy-loss spectra shifts gradually towards higher loss energy with increasing temperature. The peak eventually reaches 2.0 eV, revealing a band gap of about 1.2 eV at 810 °C. We find that a two-dimensional (2D) disordered alloy model, where the semiconducting surface is a 2D mixture of Sn and Si substitutions, is quite consistent with our experimental data.