Local symmetry breaking in stage-1 alkali-metal–graphite intercalation compounds studied by scanning tunneling microscopy

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Abstract
Scanning tunneling microscopy has been used to study surfaces of stage-1 Cs and Rb graphite intercalation compounds on the atomic scale. We have found a (2×2) superlattice as well as a one-dimensional ordering of the alkali-metal atoms corresponding to nonhexagonal (√3 ×4) and (√3 × √13 ) superlattice structures. Three rotational domains of the one-dimensional phase have been observed, inclined at 120° to each other, with sizes ranging from 10 nm to typically 60 nm. The origin of the superlattices and a transition process, based on a surface depletion of the alkali metal, are discussed.