Adsorption and diffusion of a Cl adatom on the GaAs(001)-c(8 × 2)ζ surface

Using density-functional theory we investigate the adsorption and diffusion of Cl adatoms on the ζ structure of GaAs(001) that exhibits a large (8 × 2) reconstruction. From the calculated potential-energy surface, we identify the adsorption sites and diffusion energy barriers of a single Cl adatom. The most favorable binding site is found to be the edge of the in-surface Ga dimer, lifting it above the surface. We also find that two Cl adatoms can bind at the same in-surface Ga dimer. The Cl diffusion is discussed and compared to experimental observations.