Decoding the mechanical conductance switching behaviors of dipyridyl molecular junctions
Decoding the mechanical conductance switching behaviors of dipyridyl molecular junctions
复制标题
DOI：
10.1039/d3nr00505d
复制
发表时间：
2023-06-30
期刊：
影响因子：
6.7
通讯作者：
Li，Zong-Liang
中科院分区：
文献类型：
--
作者：
Sun，Feng;Liu，Lin;Li，Zong-Liang
联吡啶分子结通常在机械调制下表现出有趣的电导开关行为，但其机制仍未完全揭示。应用基于从头算的绝热模拟方法，系统地研究了联吡啶分子结在拉伸和压缩过程中的构型演化和电子输运性质。数值结果表明，联吡啶分子结在形成过程中往往会形成特定的接触构型。在较小的电极间隙中，通过将顶层Au原子推到一边，吡啶类化合物几乎垂直地吸附在尖端电极的第二层Au上。这些特殊的接触结构导致更强的分子-电极耦合和更大的电子入射截面积，从而导致更大的破碎力和高电导。在进一步拉长分子结时，吡啶转移到了尖端电极的顶端Au原子上。顶部Au原子的额外散射显著地降低了电导，并将分子结切换到较低的导电态。实验中观察到，通过反复拉伸和压缩分子结，可以得到完美的循环电导开关。侧基中的O原子倾向于阻碍吡啶吸附在第二层金上，进而抑制联吡啶分子结的电导开关。
Dipyridyl molecular junctions often show intriguing conductance switching behaviors with mechanical modulations, but the mechanisms are still not completely revealed. By applying the ab initio-based adiabatic simulation method, the configuration evolution and electron transport properties of dipyridyl molecular junctions in stretching and compressing processes are systematically investigated. The numerical results reveal that the dipyridyl molecular junctions tend to form specific contact configurations during formation processes. In small electrode gaps, the pyridyls almost vertically adsorb on the second Au layers of the tip electrodes by pushing the top Au atoms aside. These specific contact configurations result in stronger molecule–electrode couplings and larger electronic incident cross-sectional areas, which consequently lead to large breaking forces and high conductance. On further elongating the molecular junctions, the pyridyls shift to the top Au atoms of the tip electrodes. The additional scattering of the top Au atoms dramatically decreases the conductance and switches the molecular junctions to the lower conductive states. Perfect cyclical conductance switches are obtained as observed in the experiments by repeatedly stretching and compressing the molecular junctions. The O atom in the side-group tends to hinder the pyridyl from adsorbing on the second Au layer and further inhibits the conductance switch of the dipyridyl molecular junction.