In:
Nature Communications, Springer Science and Business Media LLC, Vol. 12, No. 1 ( 2021-06-08)
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(CH 2 ) (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 ( ε r ) 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(CH 2 ) n X//electrode interface that modifies the tunnelling barrier shape. Commonly-used tunnelling models neglect localized potential drops and changes in ε r . Here, we demonstrate experimentally that $$\beta \propto 1/\sqrt{{\varepsilon }_{r}}$$ β ∝ 1 / ε r , 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.
Type of Medium:
Online Resource
ISSN:
2041-1723
DOI:
10.1038/s41467-021-23528-8
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2021
detail.hit.zdb_id:
2553671-0
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