STM investigation on interaction between superstructure and grain boundary in graphite

Interaction between superstructures and grain boundary in graphite has been investigated by STM. Through scanning for several times against the step of a terrace on the graphite substrate, a monolayer with a grain boundary can be torn apart from the terrace and rotated by a known angle 56.4 ± 0.6° against the substrate. In the monolayer, the images of neighboring domains separated by the grain boundary are completely different, with one domain showing the superstructure while the other not. The periodicity of the superstructure is measured to be 3.9 ± 0.4 nm that is correlated well with the rotation angle 56.4 ± 0.6° by the lattice mismatch induced superlattice assumption. It has been found that the misorientation angle between two domains is 4.0 ± 0.2°, resulting in overlapping with the substrate lattice in the non-superstructure domain. It thus explains satisfactorily why the superstructure ends abruptly to the grain boundary. Moreover, a moiré pattern with the periodicity of 0.4 nm has also been observed on the grain boundary and its possible origin is discussed.