电子-分子振动相互作用对分子器件稳定性和电学性质影响理论研究

Vibrational modes of molecular electronic devices are directly related to the molecular geometry and the bonding configurations at the molecule-electrode interfaces. Furthermore, electron-vibration interaction can transfer energy from the conducting electrons to local molecular vibrational modes and thus increase the effective temperature of the central molecule, which will affect the thermal stability of molecular devices. Therefore, exploring the vibrational properties of molecular devices at steady-state and the effects of electron-vibration interaction on the electronic transport and stability is an important step in molecular electronics. In this project, we will investigate the effects of the applied bias and the electric current on the molecular vibrational modes taking into account the detailed atomic structure of the molecule device, and establish the relation of the Raman spectroscopy with the electric current and the junction conductance. This is realized by employing the non-equilibrium Green's function formalism combined with density functional theory. We will also analyze quantitatively the influence of the electron-vibration and vibration-phonon interactions on the effective temperature of the central molecule and design molecular electronic devices with specific functionality and high stability, which is helpful for the progress of molecular electronics.

分子电子器件的分子振动谱不仅能够反映器件中的分子构型和分子-电极界面的连接状态，而且传导电子与分子振动自由度之间的能量传递还会改变分子的等效温度从而影响器件的稳定性。因此，分子电子器件稳态输运时的分子振动谱、电子-分子振动相互作用对其电学特性和器件稳定性影响的理论研究是分子电子学的重要研究内容。本项目以非平衡格林函数方法和密度泛函理论为主要理论计算工具，明确考虑分子电子器件的原子构型，研究外加偏压和电流对分子振动谱的影响，建立器件的电流、电导与分子拉曼光谱之间的关联；定量分析电子-分子振动相互作用和分子振动-电极声子相互作用对器件中分子等效温度的影响，设计具有特定功能并且结构稳定的分子电子器件。本项目将为分子器件电子输运特性的改进和提高提供理论分析工具，推动分子电子器件的研究深入和进一步实用化。

以非平衡格林函数和密度泛函理论为主要计算方法，研究了分子电子器件稳态输运时的器件结构与性能关系，分析了电子-分子振动相互作用对电子输运特性和器件稳定性的影响，设计了性能优异、结构稳定的分子电子器件并进行了实验制备和电学性能测试，所制备的石墨烯电极单分子场效应晶体管能够在室温下稳定工作而且具有优良的电学性能例如其电流调控可以达到一个量级以上。相关研究成果有助于分子电子器件的进一步实用化。