Imaging of liquid crystals using a tunneling microscope

Abstract

Individual organic molecules in a liquid crystal array on a graphite surface have been imaged with the scanning tunneling microscope (STM) with near-atomic resolution 1, 2. Two-dimensional order has been identified in 4-n-octy1-4’-cyanobiphenyl (8CR) and 5-nony1-2-n-nonoxylphenylpyrimidine (PYT) 909). The high resolution of the STM allows direct observation of intermolecular distances, angles and orientations. From the data, we find in the case of 803 a variety of surface phases can exist whereas for PYP 909 we find only one simple configuration. The graphite substrate appears to influence the molecules in two ways: 1) the molecular axes lie parallel to the surface so that the STM images a cross-section of the classical smectic planes; and 2) molecules of one plane are registered with those of adjacent planes, a degree of order which is not normally observed in the bulk. © 1989 SPIE.