Observation of Molecular Alignment of 3-n-Octadecylthiophene by Scanning Tunneling Microscope

The molecular alignment of an alkylthiophene, 3-n-octadecylthiophene, on highly oriented pyrolytic graphite has been studied by scanning tunneling microscopy (STM). Lateral stripes with a period of 0.42 nm and vertical stripes with one of 5.0 nm are observed and assigned to molecular alignments of alkyl chains and thiophene rings connected by "head to head", respectively. An STM image of N-n-octadecylpyrrole is also presented.