Stress-driven structural transformation of Sb-passivated Si(114)

Combined investigation of STM, high-resolution synchrotron photoemission, and density functional theory calculations allowed us to understand the Sb-induced structural-transformation of Si(114)-2 × 1. When 2 ML of Sb is deposited on Si(114)-2 × 1 at room temperature and postannealed at 500 °C, all of the surface Si atoms with dangling bonds are replaced by Sb atoms. Among one-dimensional (1D) structures consisting of Si(114)-2 × 1, such as a dimer with a 6-membered ring (D ₆) row, a rebonded-atom (R) row, and a tetramer (T) row [D ₆-R-T], the T row is split into a dimer row with a 7-membered ring (D ₇) and an R row [D ₆-R-D ₇-R]. Since the R-D ₇-R unit, a building block of Sb/Si(113)2 × 2, is under stress-balance, the Sb/Si(114)-2 × 1 surface is stressed compressively due to the extra D ₆ unit. As a result, with additional postannealing at 600 °C, two periods of this 2 × 1 [(D ₆-R-D ₇-R)-(D ₆-R-D ₇-R)] are gradually converted to 2 × 2 [(D ₆-R-D ₆-R)-(R- D ₇-R)], where the D ₆-R (115) unit is stress-balanced. The corresponding photoemission data obtained from both of the phases show that all of the surface components of the clean surface have disappeared, instead the single Sb-Si interfacial component has appeared, which indicates that the charge transfers from interfacial Si to surface Sb atoms. Finally, the density functional theory calculations have also confirmed that there are two distinct phases determined by the chemical potential of passivating Sb atoms.