Structure of alkanethiolate monolayers on Cu(100): Self-assembly on the four-fold-symmetry surface
Structure of alkanethiolate monolayers on Cu(100): Self-assembly on the four-fold-symmetry surface
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Cu(100) 上链烷硫醇单分子层的结构：四重对称表面上的自组装
DOI：
10.1021/jp015517r
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发表时间：
2001
影响因子：
3.3
通讯作者：
H. Kuroda
中科院分区：
文献类型：
--
作者：
H. Kondoh;N. Saito;F. Matsui;T. Yokoyama;T. Ohta;H. Kuroda
利用扫描隧道显微镜（STM）和X射线吸收精细结构谱（XAFS）研究了硫醇己酯在Cu（100）表面自组装膜（SAMs）的结构和生长过程。在饱和覆盖度下，硫醇盐组装成c（2 x 6）结构，沿着紧密堆积的Cu行沿着排列锯齿状链.硫醇盐的硫原子占据未重构Cu（100）表面的4重空位，最近邻的S-S距离为3.6A。这种硫吸附导致S/Cu层和烷基链层之间的大的晶格失配，因为烷基的链间距离为约100。4.5 A.然而，它是由桥接两层的S-C键的内部自由度协调的，如通过基于分子力场计算的几何优化所证实的。SAM膜的形成是很好地描述了一个两步的过程;在第一步中，一个全覆盖的单层迅速形成，其特征在于由一个高度取向，但二维无序的结构，其次是一个慢得多的演变为c（2 × 6）结构与表面扩散的硫醇盐。
We have studied the structure and growth process of hexanethiolate self-assembled monolayers (SAMs) on Cu( 100) by means of scanning tunneling microscopy (STM) and X-ray absorption fine structure (XAFS) spectroscopy. At saturated coverage, the thiolates are assembled into a c(2 x 6) structure with zigzag chains along the close-packed Cu rows. The sulfur atom of the thiolate occupies the 4-fold hollow site of the unreconstructed Cu(100) surface with a nearest-neighbor S-S distance of 3.6 A. Such sulfur adsorption results in a large lattice mismatch between the S/Cu layer and the alkyl chain layer, since the interchain distance of the alkyl group is ca. 4.5 A. However, it is reconciled by the internal degree of freedom for the S-C bond which bridges the two layers, as is confirmed by the geometrical optimization based on molecular force-field calculations. The SAM film formation is well-described by a two-step process; in the first step, a full-coverage monolayer is rapidly formed, which is characterized by a highly oriented but two-dimensionally disordered structure, followed by a much slower evolution to the c(2 x 6) structure with surface diffusion of the thiolate.