X-RAY STANDING-WAVE STUDY OF AN SB-TERMINATED GAAS(001)-(2X4) SURFACE

The Sb-Sb dimer structure of a 2 X 4 reconstructed Sb/GaAs(001) surfac e was investigated by core-level photoelectron collection mode of back reflection soft x-ray standing-wave technique. Sb atoms occupy the br idge site forming bonds with two underlying Ga atoms and form symmetri c Sb-Sb dimers lining up in the [1 (1) over bar 0] direction. The firs t-layer Sb atomic plane is estimated to be 1.81+/-0.02 Angstrom above the second-layer Ga lattice plane. The bond length of the Sb-Sb dimer on a GaAs(001) surface is estimated to be 2.95+/-0.06 Angstrom, which is longer than the reported Sb-Sb bond length for Sb/GaAs(110) surface .