TY - JOUR

T1 - σ-dominated charge transport in sub-nanometer molecular junctions

AU - Hu, Yong

AU - Zhou, Yu

AU - Ye, Jingyao

AU - Yuan, Saisai

AU - Xiao, Zongyuan

AU - Shi, Jia

AU - Yang, Yang

AU - Solomon, Gemma C.

AU - Hong, Wenjing

N1 - 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

PY - 2024

Y1 - 2024

N2 - 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.

AB - 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.

KW - Device miniaturization

KW - Flicker noise analysis

KW - Scanning tunneling microscope break junction technique

KW - Sub-nanometer molecular junction

KW - Σ-dominated charge transport

U2 - 10.1016/j.fmre.2022.06.021

DO - 10.1016/j.fmre.2022.06.021

M3 - Journal article

AN - SCOPUS:85140324975

JO - Fundamental Research

JF - Fundamental Research

SN - 2667-3258

ER -