Charge transport across insulating self-Assembled monolayers: Non-equilibrium approaches and modeling to relate current and molecular structure

Fatemeh Mirjani, Joseph M. Thijssen, George M. Whitesides, Mark A Ratner

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

This paper examines charge transport by tunneling across a series of electrically insulating molecules with the structure HS(CH2)4CONH(CH2)2R) in the form of self-Assembled monolayers (SAMs), supported on silver. The molecules examined were studied experimentally by Yoon et al. (Angew. Chem. Int. Ed. 2012, 51, 4658-4661), using junctions of the structure AgS(CH2)4CONH(CH2)2R//Ga2O3/EGaIn. The tail group R had approximately the same length for all molecules, but a range of different structures. Changing the R entity over the range of different structures (aliphatic to aromatic) does not influence the conductance significantly. To rationalize this surprising result, we investigate transport through these SAMs theoretically, using both full quantum methods and a generic, independent-electron tight-binding toy model. We find that the highest occupied molecular orbital, which is largely responsible for the transport in these molecules, is always strongly localized on the thiol group. The relative insensitivity of the current density to the structure of the R group is due to a combination of the couplings between the carbon chains and the transmission inside the tail. Changing from saturated to conjugated tail groups increases the latter but decreases the former. This work indicates that significant control over SAMs largely composed of nominally insulating groups may be possible when tail groups are used that are significantly larger than those used in the experiments of Yoon et al.1

Original languageEnglish
Pages (from-to)12428-12436
Number of pages9
JournalACS Nano
Volume8
Issue number12
DOIs
Publication statusPublished - Dec 23 2014

Fingerprint

Self assembled monolayers
Molecular structure
Charge transfer
molecular structure
Molecules
molecules
Molecular orbitals
Silver
Sulfhydryl Compounds
Current density
Carbon
thiols
Electrons
molecular orbitals
silver
current density
carbon
Experiments
sensitivity
electrons

Keywords

  • charge transport
  • current density
  • hole tunneling
  • molecular electronics
  • molecular structure
  • self-Assembled monolayers

ASJC Scopus subject areas

  • Engineering(all)
  • Materials Science(all)
  • Physics and Astronomy(all)

Cite this

Charge transport across insulating self-Assembled monolayers : Non-equilibrium approaches and modeling to relate current and molecular structure. / Mirjani, Fatemeh; Thijssen, Joseph M.; Whitesides, George M.; Ratner, Mark A.

In: ACS Nano, Vol. 8, No. 12, 23.12.2014, p. 12428-12436.

Research output: Contribution to journalArticle

Mirjani, Fatemeh ; Thijssen, Joseph M. ; Whitesides, George M. ; Ratner, Mark A. / Charge transport across insulating self-Assembled monolayers : Non-equilibrium approaches and modeling to relate current and molecular structure. In: ACS Nano. 2014 ; Vol. 8, No. 12. pp. 12428-12436.
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