Bi- and Au-Induced Reconstructions on GaAs(001)-2×4 Surface

Submonolayer Bi and Au adsorptions on the GaAs(001)-2×4 surface are investigated by scanning tunnelling microscopy, low energy electron diffraction and first-principles calculations. The 1×4 and 3×4 reconstructed surface induced by Bi and Au, respectively, are revealed and their structural models are proposed based on experiments and first-principles calculations. Moreover, the validity of the recently proposed generalized electron counting (GEC) model Phys. Rev. Lett. 97 (2006) 126103 is examined in detail by using the two surfaces. The GEC model perfectly explains the structural features, such as the characteristic short double-line structure in the Bi-1×4 surface and the 3× arrangement of four-atom Au clusters.