Sub-Band Filling, Mott-like Transitions, and Ion Size Effects in C 60 Single Crystal Electric Double Layer Transistors

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Electric double layer transistors (EDLTs) based on C60 single crystals and ionic liquid gates display pronounced peaks in sheet conductance versus gate-induced charge. Sheet conductance is maximized at electron densities near 0.5 e/C60 and is suppressed near 1 e/C60. The conductance suppression depends markedly on the choice of ionic liquid cation, with small cations favoring activated transport and essentially a complete shutdown of conductance e/C60 and larger cations favoring band-like transport, higher overall conductances at all charge densities up to 1.7 e/C60, and weaker suppression at 1 e/C60. Displacement current measurements on C60 EDLTs with small cations show clear evidence of sub-band filling at 1 e/C60, which correlates very well with the minimum in the C60 sheet conductance. Overall, the data suggest a significant Mott-Hubbard-like energy gap opens up in the surface density of states for C60 crystals gated with small cations. The causes of this energy gap may include both electron-electron repulsion and electron-cation attraction at the crystal/ionic liquid interface. The energy gap suppresses the insulator-to-metal transition in C60 EDLTs, but it can be manipulated by choice of electrolyte.

Original languageEnglish (US)
Pages (from-to)4823-4830
Number of pages8
JournalACS nano
Issue number3
StatePublished - Mar 22 2022

Bibliographical note

Funding Information:
This work was primarily supported by the MRSEC program of the National Science Foundation under Grant Number DMR-2011401. T.H. also acknowledges the National Natural Science Foundation of China Grant 62074093. C.D.F. acknowledges partial support from NSF through the National Nano Coordinated Infrastructure (NNCI) Network, under Award Number ECCS-2025124. T.H. also acknowledges support from the Qilu Young Scholars Program of Shandong University and Shandong Taishan Young Expert Program (tsqn201909027). C.D.F. thanks Merck for supplying the ionic liquids and Chris Leighton and Turan Birol of the University of Minnesota for stimulating discussions and comments on the manuscript.

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.


  • Csingle crystal
  • charge transport
  • electric double layer transistor
  • electron-ion interaction
  • ion size
  • ionic liquid
  • Mott transition
  • C single crystal

MRSEC Support

  • Primary

PubMed: MeSH publication types

  • Journal Article


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