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Molecular Self-Assembly in a Poorly Screened Environment: F4TCNQ on Graphene/BN

Molecular Self-Assembly in a Poorly Screened Environment: F4TCNQ on Graphene/BN(a) Chemical structure of F4TCNQ molecule. (b) STM and (c) nc-AFM images of a 2D F4TCNQ island on graphene/BN. Image resolves individual chemical bonds within the F4TCNQ molecules and shows that molecules within the island lie flat on the surface in a close-packed rectangular lattice.

Scientific Achievement
Charged molecules that would normally repel one another have been observed to attract each other on graphene due to a novel self-assembly mechanism

Significance and Impact
A new self-assembly mechanism should apply to other charged molecular systems involving 2D materials and provides a new route to engineer useful nanostructures

Research Details

  • Charged F4TCNQ molecules were observed to form tightly packed molecular islands on graphene supported by boron nitride.
  • Atomic force microscopy was used to investigate the atomic-scale structure of 2D molecular islands on graphene.
  • Molecular island formation was explained by a novel self-assembly mechanism for charged molecules in a poorly screened environ- ment where nanoscale work function heterogeneity exists.

H.-Z. Tsai, A. A. Omrani, S. Coh, H. Oh, S. Wickenburg, Y.-W. Son, D. Wong, A. Riss, H. S. Jung, G. D Nguyen, G. F. Rodgers, A. S. Aikawa, T. Taniguchi, K. Watanabe, A. Zettl, S. G. Louie, J. Lu, M. L. Cohen, M. F. Crommie, ACS Nano (2015)