Comparative scanning tunneling microscopy observation of a homologous series of n‐alkyloxy‐cyanobiphenyles

In scanning tunneling microscopy (STM) experiments liquid crystals (LC) do often serve as model substances for organic adsorbates on solid substrates. Especially, the group of alkyl‐cyanobiphenyle (nCB, n=number of carbon atoms in the alkyl chain) liquid crystals has been in the center of interest for a long time. In this work we present STM results of adsorbate studies of the closely related molecules of the alkyloxy‐cyanobiphenyle type (nOCB, with n=5,7,8). Under the influence of the electric field at the STM tip apex these LC molecules form well‐ordered structures, which are determined by the atomic structure of the substrate surface. This molecular ordering of a thin adsorbate layer above the substrate is investigated by STM. The results on OCBs are compared with data from x‐ray diffraction studies and with results of STM measurements of the closely related 8 CB. Both highly oriented pyrolytic graphite and molybdenum disulfide have been used as substrates.