Scanning tunneling microscopy study of ternary alkali-metal graphite intercalation compounds

Abstract

Scanning tunneling microscopy (STM) has been applied to investigate the submicrometer and atomic structure of ternary alkali-metal graphite intercalation compounds (GIC's) in a high-purity inert gas environment. Here we focus on ternary stage-1 GIC's as MM'C 8 (M, M' =K, Cs, Rb). On a submicrometer scale, we observe islands of decreased or increased apparent topographic height, suggesting an inhomogeneous alkali-metal distribution on a lateral scale of a few tens of nanometers. Variation of the local work-function as a possible explanation is discussed. On the atomic scale, both hexagonal 2x2 superlattices and one-dimensional linear structures similar to stage-1 CsC 8 and RbC 8 are observed. In addition, a novel non-hexagonal superlattice rotated at an angle of 18° respective to the graphite host lattice with a periodicity of about 1.9 nm has been observed.