Cyanobiphenyl-group alignment observed by a scanning tunneling microscope

摘要

The geometry of a nematic liquid crystal (LC), 4-n-octyl-4'-cyanobiphenyl (8CB) on the (0002) surface of graphite is studied by scanning tunneling microscopy. The tilting of cyanobiphenyl-groups on a substrate is observed. Molecular orbital calculations confirm that the molecular orbitals of neighboring molecules interact with each other. It is confirmed by the calculation between two molecules that a cyanobenzene configuration normal to the graphite surface is energetically favorable. This shows that the LC molecule alignment is determined not only by the interaction between molecules but also by its interaction with the substrate. This may provide a means of making individual molecule optical isomers.