Theory of Cs adsorption on InAs(1 1 0)

We present a first-principle study of the stable phase of the Cs-covered InAs(1 1 0) surface, in the high coverage regime. The results of our calculations reveal the formation of a novel reconstruction, compatible with one-dimensional [1 1̄ 0] Cs wires formed by adatoms at two inequivalent surface sites. The calculated electronic properties allow a microscopic understanding of the adsorption mechanism and of the wire structure. Adsorption occurs through the outward displacement of alternate surface In cations, involving complete filling of the surface state associated to their dangling bonds. The As anions participate in the global in-plane charge redistribution. The calculated structural and electronic properties compare well to recent experimental low energy electron diffraction and scanning tunneling microscopy data. The results are discussed in comparison with a variety of other alkali/semiconductor systems: while the adsorption mechanism is the same, the metal-to-substrate strain is responsible for the structural details of the adatom chain.