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Soft versus hard junction formation for alpha-terthiophene molecular wires and their charge transfer complexes

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Soft versus hard junction formation for alpha-terthiophene molecular wires and their charge transfer complexes. / Vezzoli, Andrea; Grace, Iain M.; Brooke, Carly; Nichols, Richard J.; Lambert, Colin J.; Higgins, Simon J.

In: Journal of Chemical Physics, Vol. 146, No. 9, 092307, 07.03.2017.

Research output: Contribution to journalJournal articlepeer-review

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Vezzoli, A, Grace, IM, Brooke, C, Nichols, RJ, Lambert, CJ & Higgins, SJ 2017, 'Soft versus hard junction formation for alpha-terthiophene molecular wires and their charge transfer complexes', Journal of Chemical Physics, vol. 146, no. 9, 092307. https://doi.org/10.1063/1.4969077

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Vezzoli, Andrea ; Grace, Iain M. ; Brooke, Carly ; Nichols, Richard J. ; Lambert, Colin J. ; Higgins, Simon J. / Soft versus hard junction formation for alpha-terthiophene molecular wires and their charge transfer complexes. In: Journal of Chemical Physics. 2017 ; Vol. 146, No. 9.

Bibtex

@article{b49ffa6b09ef4c9fa0d6320bef9248bd,
title = "Soft versus hard junction formation for alpha-terthiophene molecular wires and their charge transfer complexes",
abstract = "We used a range of scanning tunnelling microscopy (STM)-based methods to conduct a detailed study of single molecule junction conductance enhancement upon charge transfer complex formation, using bis(thiaalkyl) arene molecular wires as electron donors and tetracyanoethylene (TCNE) as an electron acceptor. Using the {"}hard{"} STM break junction (STM-BJ) method, in which a Au STM tip is pushed into a Au substrate and then withdrawn in the presence of molecules, we see a single, very broad, peak in the resulting conductance histogram when all data are used; the conductance enhancement is 25-fold for a terthiophene donor and 15-fold for a phenyl group. After rational data selection, in which only current-distance curves that contain a current plateau > 0.2 nm long are used in the conductance histogram, three sharper peaks are resolved in the histograms for the charge transfer complexes; two substantially lower-conductance peaks are resolved for the uncomplexed molecules. Using the {"}soft{"} STM I(s) technique, in which initial contact between tip and substrate is avoided and the current limit is about an order of magnitude lower, we were able to resolve two peaks for the uncomplexed molecules depending upon the initial set point current (i.e., tip height), one at the same value as the lower of the two data-selected STM-BJ histogram peaks and an additional peak beyond the low-current limit for the STM-BJ experiment. For the terthiophene, the low, medium, and high conductance peaks for the TCNE complex are, respectively, ca. 70, 70, and 46 times higher in conductance than the corresponding peaks for the free molecule. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license",
keywords = "CONDUCTANCE, CONDUCTIVITY, DEPENDENCE, ELECTRONICS, LENGTH",
author = "Andrea Vezzoli and Grace, {Iain M.} and Carly Brooke and Nichols, {Richard J.} and Lambert, {Colin J.} and Higgins, {Simon J.}",
year = "2017",
month = mar,
day = "7",
doi = "10.1063/1.4969077",
language = "English",
volume = "146",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "AMER INST PHYSICS",
number = "9",

}

RIS

TY - JOUR

T1 - Soft versus hard junction formation for alpha-terthiophene molecular wires and their charge transfer complexes

AU - Vezzoli, Andrea

AU - Grace, Iain M.

AU - Brooke, Carly

AU - Nichols, Richard J.

AU - Lambert, Colin J.

AU - Higgins, Simon J.

PY - 2017/3/7

Y1 - 2017/3/7

N2 - We used a range of scanning tunnelling microscopy (STM)-based methods to conduct a detailed study of single molecule junction conductance enhancement upon charge transfer complex formation, using bis(thiaalkyl) arene molecular wires as electron donors and tetracyanoethylene (TCNE) as an electron acceptor. Using the "hard" STM break junction (STM-BJ) method, in which a Au STM tip is pushed into a Au substrate and then withdrawn in the presence of molecules, we see a single, very broad, peak in the resulting conductance histogram when all data are used; the conductance enhancement is 25-fold for a terthiophene donor and 15-fold for a phenyl group. After rational data selection, in which only current-distance curves that contain a current plateau > 0.2 nm long are used in the conductance histogram, three sharper peaks are resolved in the histograms for the charge transfer complexes; two substantially lower-conductance peaks are resolved for the uncomplexed molecules. Using the "soft" STM I(s) technique, in which initial contact between tip and substrate is avoided and the current limit is about an order of magnitude lower, we were able to resolve two peaks for the uncomplexed molecules depending upon the initial set point current (i.e., tip height), one at the same value as the lower of the two data-selected STM-BJ histogram peaks and an additional peak beyond the low-current limit for the STM-BJ experiment. For the terthiophene, the low, medium, and high conductance peaks for the TCNE complex are, respectively, ca. 70, 70, and 46 times higher in conductance than the corresponding peaks for the free molecule. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

AB - We used a range of scanning tunnelling microscopy (STM)-based methods to conduct a detailed study of single molecule junction conductance enhancement upon charge transfer complex formation, using bis(thiaalkyl) arene molecular wires as electron donors and tetracyanoethylene (TCNE) as an electron acceptor. Using the "hard" STM break junction (STM-BJ) method, in which a Au STM tip is pushed into a Au substrate and then withdrawn in the presence of molecules, we see a single, very broad, peak in the resulting conductance histogram when all data are used; the conductance enhancement is 25-fold for a terthiophene donor and 15-fold for a phenyl group. After rational data selection, in which only current-distance curves that contain a current plateau > 0.2 nm long are used in the conductance histogram, three sharper peaks are resolved in the histograms for the charge transfer complexes; two substantially lower-conductance peaks are resolved for the uncomplexed molecules. Using the "soft" STM I(s) technique, in which initial contact between tip and substrate is avoided and the current limit is about an order of magnitude lower, we were able to resolve two peaks for the uncomplexed molecules depending upon the initial set point current (i.e., tip height), one at the same value as the lower of the two data-selected STM-BJ histogram peaks and an additional peak beyond the low-current limit for the STM-BJ experiment. For the terthiophene, the low, medium, and high conductance peaks for the TCNE complex are, respectively, ca. 70, 70, and 46 times higher in conductance than the corresponding peaks for the free molecule. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

KW - CONDUCTANCE

KW - CONDUCTIVITY

KW - DEPENDENCE

KW - ELECTRONICS

KW - LENGTH

U2 - 10.1063/1.4969077

DO - 10.1063/1.4969077

M3 - Journal article

VL - 146

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 9

M1 - 092307

ER -