Interplay of Collective Electrostatic Effects and Level Alignment Dictates the Tunneling Rates across Halogenated Aromatic Monolayer Junctions

Xiaoping Chen, Harshini V. Annadata, Bernhard Kretz, Michael Zharnikov, Xiao Chi, Xiaojiang Yu, David A. Egger*, Christian A. Nijhuis*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

14 Citations (Scopus)

Abstract

Predictions about the electrical conductance across molecular junctions based on self-assembled monolayers (SAMs) are often made from the SAM precursor properties. Collective electrostatic effects, however, in a densely packed SAM can override these predictions. We studied, experimentally and theoretically, molecular tunneling junctions based on thiolate SAMs with an aromatic biphenyl backbone and variable, highly polarizable halogen termini X (S-(C6H5)2X; X = H, F, Cl, Br, or I). We found that the halogen-terminated systems show tunneling rates and dielectric behavior that are independent of X despite the large change in the electronegativity of the terminal atom. Using density functional theory, we show that collective electrostatic effects result in modulations of the electrostatic potential that are strongly confined spatially along the direction of charge transport, thereby rendering the role of the halogen atoms insignificant for SAMs with conjugated backbones.
Original languageEnglish
Pages (from-to)4142-4147
JournalJournal of physical chemistry letters
Volume10
Issue number14
DOIs
Publication statusPublished - 18 Jul 2019
Externally publishedYes

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