单分子电子输运性质的设计与调控

Design and Control of Electron Transport Properties of Single Molecules

本研究通过实验结合理论研究,展示了如何利用一系列巧妙的设计与精确的控制,实现对吸附在Cu(100)表面的单个三聚氰胺分子疏运性质的有效调控。室温下三聚氰胺分子吸附到Cu(100)表面时会与表面反应脱去两个氢原子,从而与表面铜原子成键形成与表面垂直的吸附构型。分子的输运曲线表现为正负电压下对称的特征。通过扫描探针对其操控诱导了三聚氰胺分子的异构化,其电子输运特性显示出明显的整流效应。扫描探针注入的非弹性隧穿电子可以进一步诱导其顶端N-H键的可逆转动,引起电流在低电导和高电导间转换,实现了单分子机械开关效应。从而在单个分子结构上既实现整流效应又实现机械开关效应,实现了在单个分子上的双功能集成。

We demonstrate in this joint experimental and theoretical study how one can alter electron transport behavior of a single melamine molecule adsorbed on a Cu （100） surface by performing a sequence of elegantly devised and well-controlled single molecular chemical processes. It is found that with a dehydrogenation reaction,the melamine molecule becomes firmly bonded onto the Cu surface and acts as a normal conductor controlled by elastic electron tunneling. A current-induced hydrogen tautomerization process results in an asymmetric melamine tautomer,which in turn leads to a significant rectifying effect. Furthermore,by switching on inelastic multielectron scattering processes,mechanical oscillations of an N-H bond between two configurations of the asymmetric tautomer can be triggered with tuneable frequency. Collectively,this designed molecule exhibits rectifying and switching functions simultaneously over a wide range of external voltage.