SCANNING-TUNNELING-MICROSCOPY IMAGES OF A NOVEL DIMERIC LIQUID-CRYSTAL ON GRAPHITE

Scanning tunneling microscopy (STM) images of a side-by-side dimeric l iquid crystal adsorbed on graphite suggest an unusual structure for th e monolayer. Instead of the contact with the graphite being maximized, two of the alkyl tails appear to be nearly normal to the surface. Cal culations suggest that this may be due to the substitution of one of t he aromatic rings in the core, which causes an alkoxy tail to prefer a n orientation perpendicular to the aromatic core rather than the usual coplanar orientation. STM images taken at various bias voltages corre late strongly to the aromatic ''cores'' of the molecules, but do not a ppear to correlate to the highest occupied moleculear orbital or lowes t unoccupied molecular orbital.