Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
Langmuir. 2013 Feb 19;29(7):2250-7. doi: 10.1021/la304902y. Epub 2013 Feb 6.
We investigated the dynamics of decanethiol self-assembled monolayers on Au(111) surfaces using time-resolved scanning tunneling microscopy at room temperature. The expected ordered phases (β, δ, χ*, and φ) and a disordered phase (ε) were observed. Current-time traces with the feedback loop disabled were recorded at different locations on the surface. The sulfur end group of the decanethiolate molecule exhibits a stochastic two-level switching process when the molecule is adsorbed in a (local) β phase registry. This two-level process is attributed to the diffusion of the Au-thiolate complex between two adjacent adsorption sites. The irregular current jumps in the current-time traces recorded on the tails of decanethiolate molecules in the ordered β, δ, and χ* phases are ascribed to wagging of the alkyl tails. Finally, the disordered phase is characterized by even larger current jumps, which indicates that the tail of the decanethiolate flips up occasionally and makes contact with the tip. Our experiments reveal that the massive dynamics of the self-assembled monolayer is due to diffusion of decanethiol-Au complexes, rather than the diffusion of decanethiolate molecules.
我们使用室温下的时间分辨扫描隧道显微镜研究了在 Au(111)表面上的癸硫醇自组装单层的动力学。观察到了预期的有序相（β、δ、χ和φ）和无序相（ε）。在表面的不同位置记录了反馈环路关闭时的电流-时间迹线。当分子在（局部）β相登记处吸附时，癸硫醇盐分子的硫端基表现出随机的两级开关过程。这个两级过程归因于 Au-硫醇配合物在两个相邻吸附位之间的扩散。在有序β、δ和χ相中记录的癸硫醇盐分子尾部的不规则电流跃变归因于烷基尾部的摆动。最后，无序相的特征是甚至更大的电流跃变，这表明癸硫醇盐的尾部偶尔翻转并与尖端接触。我们的实验表明，自组装单层的大规模动力学是由于癸硫醇-Au 配合物的扩散，而不是癸硫醇盐分子的扩散。
