Abstract
AbstractWe 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 $$\beta \propto 1/\sqrt{{\varepsilon }_{r}}$$
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.
Publisher
Springer Science and Business Media LLC
Subject
General Physics and Astronomy,General Biochemistry, Genetics and Molecular Biology,General Chemistry
Reference69 articles.
1. Shah, A. et al. Electron transfer in peptides. Chem. Soc. Rev. 44, 1015–1027 (2015).
2. Vilan, A., Aswal, D. & Cahen, D. Large-area, ensemble molecular electronics: motivation and challenges. Chem. Rev. 117, 4248–4286 (2017).
3. Jortner, J., Nitzan, A. & Ratner, M. A. in Introducing Molecular Electronics (eds. Cuniberti, G. et al.) 13–54 (Springer, 2005).
4. Jia, C. & Guo, X. Molecule–electrode interfaces in molecular electronic devices. Chem. Soc. Rev. 42, 5642–5660 (2013).
5. Metzger, R. M. Unimolecular electronics. Chem. Rev. 115, 5056–5115 (2015).
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