Feng Anni, Hou Songjun, Yan Juanzhu, Wu Qingqing, Tang Yongxiang, Yang Yang, Shi Jia, Xiao Zong-Yuan, Lambert Colin J, Zheng Nanfeng, Hong Wenjing
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, 361005 Xiamen, China.
Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom.
J Am Chem Soc. 2022 Aug 31;144(34):15680-15688. doi: 10.1021/jacs.2c05856. Epub 2022 Aug 19.
Quantum-tunneling-based nanoelectronics has the potential for the miniaturization of electronics toward the sub-5 nm scale. However, the nature of phase-coherent quantum tunneling leads to the rapid decays of the electrical conductance with tunneling transport distance, especially in organic molecule-based nanodevices. In this work, we investigated the conductance of the single-cluster junctions of a series of atomically well-defined silver nanoclusters, with varying sizes from 0.9 to 3.0 nm, using the mechanically controllable break junction (MCBJ) technique combined with quantum transport theory. Our charge transport investigations of these single-cluster junctions revealed that the conductance grows with increasing cluster size. The conductance decay constant was determined to be ∼-0.4 nm, which is of opposite sign to that of organic molecules. Comparison between experiment and theory reveals that although charge transport through the silver single-cluster junctions occurs via phase-coherent tunneling, this is compensated by a rapid decrease in the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO gap) with size and the increase in the electrode-cluster coupling, which results in their conductance increase up to lengths of ∼3.0 nm. These results demonstrate that such families of nanoclusters provide unique bottom-up building blocks for the fabrication of nanodevices in the sub-5 nm size range.
基于量子隧穿的纳米电子学具有将电子产品小型化至低于5纳米尺度的潜力。然而，相位相干量子隧穿的特性导致电导随着隧穿传输距离迅速衰减，尤其是在基于有机分子的纳米器件中。在这项工作中，我们使用机械可控断裂结（MCBJ）技术结合量子输运理论，研究了一系列尺寸从0.9到3.0纳米不等、原子结构明确的银纳米团簇的单团簇结的电导。我们对这些单团簇结的电荷输运研究表明，电导随着团簇尺寸的增加而增大。确定电导衰减常数约为-0.4纳米，这与有机分子的符号相反。实验与理论的比较表明，尽管通过银单团簇结的电荷输运是通过相位相干隧穿发生的，但这被最高占据分子轨道与最低未占据分子轨道之间的能隙（HOMO-LUMO能隙）随尺寸的迅速减小以及电极-团簇耦合的增加所补偿，这导致它们的电导增加至约3.0纳米的长度。这些结果表明，此类纳米团簇家族为制造尺寸在5纳米以下的纳米器件提供了独特的自下而上的构建块。
