Au(111)面混合链长二硫醚分子自组装薄膜结构及电子传导特性的研究

Surface and interface structures of dislphide self-assembleds monolayer(SAMs）/Au(111) have attracted a significant level of attention in many years. Recent experimental research discovered the existence of a (3×4）structure at the interface between short chain (C<3) molecules and the Au(111) substrate. This new discovery has led to interesting debates around the true atomic scale structure of SAMs because of the "established"(√3×√3)R30^0/c(4×2) phase which has been known to the community for three decades. The most recent works in this area suggest that the Van deer Waals force between the molecular chains plays a far more important role in self-assembly than that has been known. In this proposal, we will concentrate on the surface and interface structure of mixed-chain-length dislphide SAMs. We will use the scanning tunnelling microscope (STM) and other surface science experimental techniques to investigate surface structure from different types of molecule units. By varying the strength of the Van deer Waals force between different molecular chains, we will analyze the guiding principles in phase transitions of SAMs. The fundamental studies will naturally lead to the exploration of physical properties of SAMs, and the application of such molecular monolayers in molecular devices, quantum structures and bio-sensing and medical diagnosis.

Au（111）面二硫醚分子自组装薄膜表面与内界面结构是近年来的研究热点。大量研究结果表明短链双硫自组装薄膜表面（3×4）饱和吸附结构的存在，而(3×4)，(√3×√3)R30^0/c(4×2)饱和吸附结构之间的争议也引起研究人员对分子链间范德华力与烷基硫醇自组装薄膜表面结构特性之间关系的重视。本研究以混合链长二硫醚体系自主装薄膜为研究对象，利用扫描隧道显微镜（STM）等表征手段，观测分析不同链长自组装薄膜饱和吸附结构特性，电子传导与相变关系。通过改变分子链间范德华作用力的大小来分析该体系自组装薄膜与Au（111）面内界面结构变化规律，从而解决Au（111）面双硫吸附模式自组装薄膜本征结构，变化相结构和过度相结构之间的争议，结合理论计算构建完整的薄膜表面结构变化体系。对完善该体系自组装薄膜表面结构相变机理，及控制单分子器件能隙与电子信号传导，生物薄膜与无机薄膜的制备等应用领域具有重要意义。

本项目以混合链长二硫醚体系分子即烷基硫醇分子在Au（111）表面的结构及电子传导特性为研究主题。利用扫描探针显微镜（STM）等表征手段，对该体系分子中长链及短链分子在Au（111）所形成的饱和及条状相结构进行了结构分析，通过不同链长分子在不扫描条件下分子官能团的电子态密度变化，了解了不同分子电子态密度信息。在结构分析过程中确定了烷基硫醇分子在Au（111）表面的双硫模式的内界面结构，并通过使用热脱附法掌握了不同链长分子在改变薄膜表面分子范德华力作用下其内界面结构的变化规律，从而构建了混合链长烷基硫醇分子在Au（111）表面的结构模型。对完善该体系自组装薄膜表面结构相变机理，及控制单分子器件能隙与电子信号传导，生物薄膜与无机薄膜的制备等应用领域起到了重要作用。