Visible mechanism of liquid crystals on graphite under scanning tunneling microscopy
- 31 December 1990
- journal article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 57 (27) , 2907-2909
- https://doi.org/10.1063/1.103749
Abstract
Liquid crystals on graphite have been observed by scanning tunneling microscopy. Although an isolated 4-n-octyl-4′-cyanobiphenyl (8CB) molecule shows a wide 11 eV energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), its image could be obtained by tunneling bias around 800 mV far below this energy gap. The fact that 8CB with a large energy gap could be imaged was confirmed by a spectroscopic measurement. This LC molecule visualizing mechanism is interpreted from one viewpoint as the result of energy level shift possibly caused by molecule-substrate interaction and from another viewpoint as the result of periodic molecules forming an energy band.Keywords
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