Atomic geometry and probability distribution of self-assembled Cs nanowires at InAs(110) surface

Cesium adsorbs on the InAs~110! surface in the form of long chains extending for several hundreds angstroms along the @11I 0# direction, leading to a (23n) periodicity, with n depending on the mean distance between the alkali chains. We have investigated the evolution of the (23n) superstructure as a function of coverage and the statistical distribution of the Cs chains by means of grazing-incidence x-ray diffraction and low-energy electron diffraction. The atomic geometry has been fully determined: each Cs chain is constituted by two Cs adatoms with different adsorption sites. The minimum Cs-Cs distance within the chain is 6.9 Å, much larger than the Cs-Cs bond length in bcc bulk metallic Cs.