σ-dominated charge transport in sub-nanometer molecular junctions
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Quantum tunneling conductance of molecular junctions originates from the charge transport through the π-orbitals (π-transport) and the σ-orbitals (σ-transport) of the molecules, but the σ-transport can not be observed due to the more rapid decay of the tunneling conductance in the σ-system compared to that in the π-system. Here, we demonstrate that dominant σ-transport can be observed in π-conjugated molecular junctions at the sub-nanometer scale using the scanning tunneling microscope break junction technique (STM-BJ). We have found that the conductance of meta-connected picolinic acid, which mainly occurs by σ-transport, is ∼35 times higher than that of its para-isomer, which is entirely different from what is expected from π-transport through these systems. Flicker noise analysis reveals that the transport through the meta-connection exhibits more through-bond transport than the para-counterpart and density functional theory (DFT) shows that the σ-system provides the dominant transport path. These results reveal that the σ-electrons, rather than the π-electrons, can dominate charge transport through conjugated molecular junctions at the sub-nanometer scale, and this provides a new avenue toward the future miniaturization of molecular devices and materials.
Original language | English |
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Journal | Fundamental Research |
ISSN | 2667-3258 |
DOIs | |
Publication status | Accepted/In press - 2024 |
Bibliographical note
Funding Information:
This work was supported by the National Natural Science Foundation of China (Grants No. 21722305 , 21673195 , 21973079 , and 21703188 ), the National Key R&D Program of China (Grant No. 2017YFA0204902 ), and the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2020A151511106 ).
Publisher Copyright:
© 2022
- Device miniaturization, Flicker noise analysis, Scanning tunneling microscope break junction technique, Sub-nanometer molecular junction, Σ-dominated charge transport
Research areas
ID: 338440880