Zhao Zhikai, Guo Chenyang, Ni Lifa, Zhao Xueyan, Zhang Surong, Xiang Dong
Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology Institute of Modern Optics, Nankai University, Tianjin 300350, China.
Nanoscale Horiz. 2021 May 4;6(5):386-392. doi: 10.1039/d1nh00031d.
We developed a method based on the mechanically controllable break junction technique to investigate the electron transport properties of single molecular junctions upon fiber waveguided light. In our strategy, a metal-coated tapered optical fiber is fixed on a flexible substrate, and this tapered fiber serves as both the optical waveguide and metal electrodes after it breaks. For an imidazole bridged single-molecule junction, two probable conductance values below 1G0 are observed. The higher value shows an approximately 40% enhancement under illumination, while the lower one does not show distinguishable difference under illumination. Theoretical calculations reveal these two conductance values resulting from the imidazole monomer junction and the imidazole dimer junction linked via a hydrogen bond, respectively. In imidazole monomer junctions, the absorption of a single photon strongly shifts the transmission function resulting in optical-induced conductance enhancement. In contrast, the transmission function of imidazole dimer junctions remains at the same level in the bias window despite the light illumination. This work provides a robust experimental framework for studying the underlying mechanisms of photoconductivity in single-molecule junctions and offers tools for tuning the optoelectronic performance of single-molecule devices in situ.
我们开发了一种基于机械可控断裂结技术的方法，用于研究单分子结在光纤波导光作用下的电子传输特性。在我们的策略中，一根涂有金属的锥形光纤固定在柔性基板上，这根锥形光纤在断裂后既作为光波导又作为金属电极。对于咪唑桥连的单分子结，观察到两个低于1G0的可能电导值。较高的值在光照下显示出约40%的增强，而较低的值在光照下没有显示出明显差异。理论计算表明，这两个电导值分别由咪唑单体结和通过氢键连接的咪唑二聚体结产生。在咪唑单体结中，单个光子的吸收强烈地改变了传输函数，导致光诱导电导增强。相比之下，尽管有光照，咪唑二聚体结的传输函数在偏置窗口中仍保持在同一水平。这项工作为研究单分子结中光电导的潜在机制提供了一个强大的实验框架，并为原位调节单分子器件的光电性能提供了工具。
