Voltage-dependent scanning tunneling microscopy images of liquid crystals on graphite

Abstract

Voltage-dependent images of liquid crystals on graphite were observed in air by scanning tunneling microscopy (STM). Molecular rows of liquid crystals and the atomic pattern of the graphite substrate were imaged with high (above 1 V) and low (below 0.1 V) bias voltages, respectively. Patterns of molecules, grain boundaries, and distinguishable defects of the liquid crystal arrangement were reproduced even after imaging the substrate in the same area. This indicates that the graphite lattice can be seen by STM without touching or disturbing the adsorbed molecules on it. A resonant tunneling model is proposed to explain the phenomenon.