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Title: A single atom change turns insulating saturated wires into molecular conductors
Authors: Chen, Xiaoping 
Kretz, Bernhard
Adoah, Francis
Nickle, Cameron
Chi, Xiao 
Yu, Xiaojiang 
del Barco, Enrique
Thompson, Damien
Egger, David A.
Nijhuis, Christian A. 
Issue Date: 8-Jun-2021
Publisher: Nature Research
Citation: Chen, Xiaoping, Kretz, Bernhard, Adoah, Francis, Nickle, Cameron, Chi, Xiao, Yu, Xiaojiang, del Barco, Enrique, Thompson, Damien, Egger, David A., Nijhuis, Christian A. (2021-06-08). A single atom change turns insulating saturated wires into molecular conductors. Nature Communications 12 (1) : 3432. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: We present an efficient strategy to modulate tunnelling in molecular junctions by changing the tunnelling decay coefficient, β, by terminal-atom substitution which avoids altering the molecular backbone. By varying X = H, F, Cl, Br, I in junctions with S(CH2)(10-18)X, current densities (J) increase >4 orders of magnitude, creating molecular conductors via reduction of β from 0.75 to 0.25 Å−1. Impedance measurements show tripled dielectric constants (εr) with X = I, reduced HOMO-LUMO gaps and tunnelling-barrier heights, and 5-times reduced contact resistance. These effects alone cannot explain the large change in β. Density-functional theory shows highly localized, X-dependent potential drops at the S(CH2)nX//electrode interface that modifies the tunnelling barrier shape. Commonly-used tunnelling models neglect localized potential drops and changes in εr. Here, we demonstrate experimentally that β∝1/εr, suggesting highly-polarizable terminal-atoms act as charge traps and highlighting the need for new charge transport models that account for dielectric effects in molecular tunnelling junctions. © 2021, The Author(s).
Source Title: Nature Communications
ISSN: 2041-1723
DOI: 10.1038/s41467-021-23528-8
Rights: Attribution 4.0 International
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