Sorbonne Universités, UPMC Univ Paris 06, UMR 7614, Laboratoire de Chimie Physique Matière et Rayonnement, 4 place Jussieu, 75005 Paris, France.
Nanoscale. 2018 Feb 1;10(5):2371-2379. doi: 10.1039/c7nr06132c.
The patterning of silicon surfaces by organic molecules emerges as an original way to fabricate innovative nanoelectronic devices. In this regard, we have studied how a diamine, N,N,N',N'-tetramethylethylenediamine (TMEDA, (CH)N-[CH]-N(CH)), chelates the silicon dimers of the Si(001)-2 × 1 surface. Starting from very low coverage to surface saturation (at 300 K), we used real-time scanning tunneling microscopy (STM) in a scanning-while-dosing approach. The images show that the molecules can adopt two bonding configurations: the cross-trench (CT) configuration by bridging two adjacent dimer rows, and the end-bridge (EB) configuration by chelating two adjacent dimers in the same row. However, while CT dominates over EB at low coverage, the percentage of EB adducts steadily increases, until it becomes largely dominant at high molecular coverage. Above a critical coverage θ of ∼0.13 monolayer (ML), a sudden change in the molecular imprints is seen, likely due to a change in the tunneling conditions. The EB stapling of two adjacent dimers in a row via a dual-dative bond (as shown by XPS) is achieved efficiently by the TMEDA molecule with a very high chemical selectivity. The EB is a unique configuration in amine adsorption chemistry, as it leads to the formation of a pair of first-neighbor, doubly-occupied dangling bonds. Further reactivity of the EB site with other molecules remains to be explored, and possible reaction schemes are envisaged.
通过有机分子对硅表面进行图案化，成为制造创新型纳米电子器件的一种原始方法。在这方面，我们研究了二胺 N,N,N',N'-四甲基乙二胺（TMEDA，（CH）N-[CH]-N(CH)）如何螯合 Si(001)-2×1 表面的硅二聚体。从非常低的覆盖度到表面饱和（在 300 K 时），我们使用了实时扫描隧道显微镜（STM）在扫描的同时进样方法。这些图像表明，分子可以采用两种键合构型：交叉沟（CT）构型，通过桥接两个相邻的二聚体行；端桥（EB）构型，通过螯合同一行中的两个相邻二聚体。然而，在低覆盖度时 CT 构型占主导地位，而 EB 加合物的比例稳步增加，直到在高分子覆盖度时占据主导地位。在临界覆盖度θ约为 0.13 单层（ML）以上时，分子印记突然发生变化，可能是由于隧道条件的变化。TMEDA 分子通过双配位键（如 XPS 所示）有效地将两个相邻二聚体在同一行中钉扎，具有非常高的化学选择性。EB 是胺吸附化学中的一种独特构型，因为它导致形成一对第一近邻、双占据的悬键。EB 位点与其他分子的进一步反应性仍有待探索，并设想了可能的反应方案。
