Charge Transport Mechanisms in Oligothiophene Molecular Junctions Studied by Electrical Conductance and Thermopower Measurements

  • See Kei Lee
  • Ryo Yamada
  • Tatsuhiko Ohto
  • Shoji Tanaka
  • Hirokazu TadaEmail author
Conference paper
Part of the Advances in Atom and Single Molecule Machines book series (AASMM)


Understanding charge transport mechanism of single-molecule–metal–molecule junctions is important in the field of molecular electronics. Till now, most of the reported works focused on small molecules, where tunneling transport dominates the charge transport. As the length of the molecule increases, the charge transport is expected to show a transition from tunneling to hopping. In this work, we performed a comprehensive investigation on oligothiophene molecules. We have measured the temperature dependence of electrical conductance and thermopower of oligothiophene molecular junctions with molecular lengths ranging from 2.2 nm (5T-di-SCN) to 7 nm (17T-di-SCN) using the homebuilt scanning tunneling microscope. The conductance measurement results reveal that the dominant charge transport for oligothiophene changed from tunneling to hopping transport at molecular length of ca. 5 nm. In addition, the thermopower for all the oligothiophene molecules was found to be positive, indicating the transport of charge carrier through the highest occupied molecular orbital level.


Electrical conductance Thermopower Molecular junctions Oligothiophenes Charge transport 



This work was supported by JSPS KAKENHI Grant Numbers JP20343741, JP15K13673 and JP25110012. L.S.K. would like to thank Henrique Rosa Testai for assistance in the thermoelectric experiments.


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  • See Kei Lee
    • 1
  • Ryo Yamada
    • 1
  • Tatsuhiko Ohto
    • 1
  • Shoji Tanaka
    • 2
  • Hirokazu Tada
    • 1
    Email author
  1. 1.Graduate School of Engineering ScienceOsaka UniversityToyonakaJapan
  2. 2.Research Center for Molecular Scale NanoscienceInstitute for Molecular ScienceOkazakiJapan

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