Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508 TA Utrecht, The Netherlands.
Institute of Physics, Czech Academy of Sciences , Cukrovarnická 10, 1862 53 Prague, Czech Republic.
ACS Nano. 2016 Sep 27;10(9):8517-25. doi: 10.1021/acsnano.6b03644. Epub 2016 Aug 16.
Scanning tunneling microscopy and atomic force microscopy can provide detailed information about the geometric and electronic structure of molecules with submolecular spatial resolution. However, an essential capability to realize the full potential of these techniques for chemical applications is missing from the scanning probe toolbox: chemical recognition of organic molecules. Here, we show that maps of the minima of frequency shift-distance curves extracted from 3D data cubes contain characteristic contrast. A detailed theoretical analysis based on density functional theory and molecular mechanics shows that these features are characteristic for the investigated species. Structurally similar but chemically distinct molecules yield significantly different features. We find that the van der Waals and Pauli interaction, together with the specific adsorption geometry of a given molecule on the surface, accounts for the observed contrast.
扫描隧道显微镜和原子力显微镜可以提供有关分子的几何和电子结构的详细信息，具有亚分子空间分辨率。然而，对于化学应用，扫描探针工具包中缺少实现这些技术全部潜力的一个基本功能：对有机分子的化学识别。在这里，我们表明从 3D 数据立方体中提取的频率位移-距离曲线的最小值图包含特征对比度。基于密度泛函理论和分子力学的详细理论分析表明，这些特征是所研究物种的特征。结构相似但化学性质不同的分子会产生明显不同的特征。我们发现，范德华力和泡利相互作用，以及给定分子在表面上的特定吸附几何形状，决定了观察到的对比度。
