Atomic structure of the low-coverage(2×2)phases of Al, Ga, and In on Ge(001)

Abstract

Using first-principles total-energy calculations, we have studied the structural properties of the low coverage $(2\mathrm{}\times 2)$ phases of Al, Ga, and In on the (001) surface of Ge. In all three cases, the structure is characterized by the formation of ad-atom dimers in the top layer. Two different models have been investigated: in the first one, the ad-dimers are parallel to the substrate Ge dimers, while in the second, they grow orthogonally. Our calculations favor the parallel ad-dimer model in all three surfaces.