Scanning tunneling microscopy (STM) is a powerful tool for observing organic molecules in real space. In this study, five similar ferroelectric liquid crystal (FLC) materials (four unsaturated isomers and the saturated parent) adsorbed on graphite were examined by scanning tunneling microscopy as neat compounds and as mixtures. The unit cells of adsorbed monolayers formed by the mixtures showed distinct differences from the unit cells of the pure compounds, suggesting that mixed monolayers were formed. The saturated compound formed two structures having different unit cells, and it appeared that the difference in energies was very small. Changing the location of the double bond had no observable effect on the adsorbed monolayers, and the isolated double bonds were not observed.