Thermopower of amine-gold-linked aromatic molecular junctions from first principles

Su Ying Quek, Hyoung Joon Choi, Steven G. Louie, Jeffrey B. Neaton

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71 Citations (Scopus)

Abstract

Using a self-energy corrected scattering-state approach based on density functional theory (DFT), we explain recent measurements of the thermopower or the Seebeck coefficient, S, for oligophenyldiamine-gold single-molecule junctions and show that they are consistent with separate measurements of their electrical conductance, G. Our calculations with self-energy corrections to the DFT electronic states in the junction predict low-bias S and G values in good quantitative agreement with experiments. We find S varies linearly with the number of phenyls N, with a gradient βS of 2.1 μV/K, in excellent agreement with experiment. In contrast, DFT calculations without self-energy corrections overestimate both S and βS (with a DFT value for βS three times too large). WhileβS is found to be a robust quantity independent of junction geometry, the computed values of S show significant sensitivity to the contact atomic structureOmore so than the computed values of G. This observation is consistent with the experimentally measured spreads in S and G for amine-Au junctions. Taken together with previous computations of the electrical conductance (as reported in Quek, S. Y.; et al., Nano Lett. 2009, 9, 3949), our calculations of S conclusively demonstrate, for the first time, the consistency of two complementary yet distinct measurements of charge transport through single-molecule junctions and substantiate the need for an accurate treatment of junction electronic level alignment to describe off-resonant tunneling in these junctions.

Original languageEnglish
Pages (from-to)551-557
Number of pages7
JournalACS Nano
Volume5
Issue number1
DOIs
Publication statusPublished - 2011 Jan 25

All Science Journal Classification (ASJC) codes

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

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