Structure of Zn adsorption on GaAs(001)-(2x4)

The atomic structures of four possible models for the adsorption of Zn on G aAs(001)-(2 x 4) are investigated by means of a first-principles pseudopote ntial technique. Our calculations suggest that Zn atoms adsorb preferential ly in trench (third layer) sites. All structures are characterized by the b reaking of the arsenic dimer and the formation of two mixed dimers in the v ertical plane containing the original As-As dimer. The Zn atom lies 0.16 An gstrom higher than the As atoms, and the mixed dimer has a bond length of 2 .31 Angstrom. All other structural features for the four models studied (e. g., minimum interplanar distance, and remaining As dimer bond lengths) reta in the characteristics of the free surface. (C) 2000 American Institute of Physics. [S0003-6951(00)04525-3].