The binding and migration paths of an isolated Au adatom on the GaAs (001)-β2(2 x 4) reconstructed surface were investigated by means of first-principles total energy calculations, using the Car-Parrinello scheme. The potential energy surface which was calculated for the Au adatom showed that the most important Au binding sites were located at short-bridge sites next to the As-As dimers on the surface. Similar binding sites were found for Ga adatoms on the same surface. However, the Au chemical binding was different to that of Ga. The Ga adatoms formed strong covalent Ga-As bonds, having a marked ionic character, when interacting with As dimers. Meanwhile, the Au-dimer interaction was characterized by the formation of weaker, purely covalent, Au-As bonds. Therefore, Au adatoms did not break As-As dimers; unlike the case of Ga adatoms. The characteristics of the Au binding also accounted for an anisotropic Au migration which appeared to be faster along the dimer rows than perpendicular to them.

Binding and Migration Paths of Au Adatoms on the GaAs(001) Surface. A.A.Bonapasta, F.Buda: Physical Review B, 2002, 65[4], 045308 (9pp)