ELECTRONIC BAND-STRUCTURE OF THE 2-DIMENSIONAL SURFACE-STATE BANDS OF THE (1X1) AND (1X2) PHASES OF BI/GASB(110)

The surface-state bands of the (1 X 1) and (1 X 2) phases of Bi/GaSb(110) have been probed using angle-resolved ultraviolet photoemission spectroscopy with synchrotron radiation. Four Bi-induced surface-state bands have been identified for both the (1 X 1) and the (1 X 2) phases. The bands with the lowest binding energies (S(I) and S(II)) have been attributed to intrachain bonding in the Bi overlayer and the higher-binding-energy bands (S(III) and S(IV)) to overlayer states involved in the back bonding of the overlayer to the substrate. Based on initial-state dispersion measurements, we conclude that the Bi chains in the epitaxial overlayer remain intact throughout the phase transition. We propose a model for the overlayer structure of the (1 X 2) phase of Bi/GaSb(110).