Hydrogen-induced reconstruction of the GaP(001) surface studied by scanning tunneling microscopy

We report results of a scanning tunneling microscopy investigation on the reconstruction of GaP(001) surfaces. We have observed a 4×2 structure, accompanied locally with c(8×2) domains, at a surface prepared by using ion sputtering and annealing method. On the contrary, both 2×4 [with local c(2×8)] and 4×2 [with local c(8×2)] structures are obtained by hydrogenation followed by annealing. The former consists of a unit structure of three P dimers plus one dimer vacancy, whereas the latter is a parallel arrangement of zig–zag-chained structures along the [110] direction. It has been shown that the surface hydrogenation before annealing induces new types of reconstruction.