Carbon induced (3×3)R30° reconstruction on Si(1 1 1) surface: a theoretical study

Various atomic structural models of recently observed carbon induced (3×3)R30° reconstruction on Si(1 1 1) surface are studied by first-principles calculations. It is found that among the four possible configurations C–T4, C–H3, C–S5 and C–S4, the most stable one is C–S5, which consists of a substitutional carbon atom directly below the Si adatom at T4 site. The stability of the C–S5 configuration is attributed to the relief of the stress caused by the short Si–C bond. The electronic structures of thermodynamically stable configuration C–S5 and the kinetically favored C–T4 configuration are studied. The calculated electronic structures show that both C–S5 and C–T4 surfaces are metallic. Based on the calculated STM images at different biases and the calculated density of states, we provide a scheme to distinguish which model is observed in the experiments.