Bismuth on GaSb(110): Structural determination of the 1x1 and 1x2 phases by surface X-ray diffraction

The surface geometry of the 1 x 1 and 1 x 2 phases of bismuth on GaSb(110) has been determined using surface X-ray diffraction with synchrotron radiation. The bismuth atoms form zigzag chains along the [1(1) over bar 0] direction of the substrate. For the 1 x 1 phase four different registries of the bismuth chains with respect to the GaSb(110) substrate are possible. It was found that only the epitaxial continued layer structure was in good agreement with the experimental data. In the 1 x 2 reconstruction every second zigzag chain in the uppermost substrate layer is missing. The reconstructed surface is terminated with a full monolayer of Ri atoms which also form zigzag chains. The Ri atoms in the chains bond alternately to the first and second layer substrate atoms and the Bi chains are inclined at 34 degrees to the surface. This new structural model explains the higher thermal stability of the 1 x 2 phase compared to that of the 1 x 1 phase.