Isshiki Yuji, Fujii Shintaro, Nishino Tomoaki, Kiguchi Manabu
Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 W4-10 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
Phys Chem Chem Phys. 2020 Feb 26;22(8):4544-4548. doi: 10.1039/c9cp06487g.
A single-molecule junction of 1,4-di(4-pyridyl)benzene (DPB) was prepared in a nano-gap between two Au electrodes using the scanning tunnelling microscopy-based break junction method (STM-BJ). Electric conductance and current versus bias voltage (I-V) measurements during the pulling and pushing processes of DPB single-molecule junctions revealed that high (H) and low (L) conductance states formed in both the pulling and pushing processes. Analysis of the I-V curves based on a single-level model indicated that the difference in conductivity of the H and L states mainly arises from high and low metal-molecule electric coupling in the junction. We demonstrated the controllable formation of H and L conductance states by simply tuning the velocity of electrode displacement in the pushing process. In the pulling process, both H and L states formed regardless of the velocity (v) of electrode displacement, while in the pushing process, H and L states could be selectively fabricated by using low (v = 16 nm s-1) and high (v = 64 nm s-1) velocities of displacement, respectively. This study provides a simple approach to selectively fabricate high and low conductance states by fine tuning of the electrode displacement.
使用基于扫描隧道显微镜的断结方法（STM-BJ），在两个金电极之间的纳米间隙中制备了1,4-二（4-吡啶基）苯（DPB）的单分子结。在DPB单分子结的拉伸和推压过程中进行的电导和电流-偏置电压（I-V）测量表明，在拉伸和推压过程中均形成了高（H）和低（L）电导状态。基于单能级模型对I-V曲线的分析表明，H态和L态电导率的差异主要源于结中金属-分子电耦合的高低。我们通过在推压过程中简单地调节电极位移速度，证明了H态和L态的可控形成。在拉伸过程中，无论电极位移速度（v）如何，都会形成H态和L态，而在推压过程中，分别使用低（v = 16 nm s-1）和高（v = 64 nm s-1）位移速度可以选择性地制造H态和L态。这项研究提供了一种通过微调电极位移来选择性制造高电导态和低电导态的简单方法。
