σ-dominated charge transport in sub-nanometer molecular junctions  

作　　者：Yong Hu Yu Zhou Jingyao Ye Saisai Yuan Zongyuan Xiao Jia Shi Yang Yang Gemma C.Solomon Wenjing Hong 

机构地区：[1]State Key Laboratory of Physical Chemistry of Solid Surfaces,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China [2]Shenzhen Research Institute of Xiamen University,Shenzhen 518000,China [3]Nano-Science Center and Department of Chemistry,University of Copenhagen,Copenhagen DK-2100,Denmark

出　　处：《Fundamental Research》2024年第5期1128-1136,共9页自然科学基础研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(21722305,21673195,21973079,and 21703188);the National Key R&D Program of China(2017YFA0204902);the Guangdong Basic and Applied Basic Research Foundation(2020A151511106).

摘　　要：Quantum tunneling conductance of molecular junctions originates from the charge transport through theπ-orbitals(π-transport)and theσ-orbitals(σ-transport)of the molecules,but theσ-transport can not be observed due to the more rapid decay of the tunneling conductance in theσ-system compared to that in theπ-system.Here,we demonstrate that dominantσ-transport can be observed inπ-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 byσ-transport,is∼35 times higher than that of its para-isomer,which is entirely different from what is expected fromπ-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 theσ-system provides the dominant transport path.These results reveal that theσ-electrons,rather than theπ-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.

关 键 词：Sub-nanometer molecular junction σ-dominated charge transport Scanning tunneling microscope break junction technique Flicker noise analysis Device miniaturization 

分 类 号：O46[理学—电子物理学]