ELECTRONIC BAND-STRUCTURE OF THE 2-DIMENSIONAL SURFACE-STATE BANDS OFTHE (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(1 10) have been probed using angle-resolved ultraviolet photoemission sp ectroscopy with synchrotron radiation. Four Bi-induced surface-state b ands 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-b inding-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 e pitaxial overlayer remain intact throughout the phase transition. We p ropose a model for the overlayer structure of the (1 X 2) phase of Bi/ GaSb(110).