Mousley Philip J, Rochford Luke A, Ryan Paul T P, Blowey Philip, Lawrence James, Duncan David A, Hussain Hadeel, Sohail Billal, Lee Tien-Lin, Bell Gavin R, Costantini Giovanni, Maurer Reinhard J, Nicklin Christopher, Woodruff D Phil
Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
Chemistry Department, University of Birmingham, University Road, Birmingham B15 2TT, U.K.
J Phys Chem C Nanomater Interfaces. 2022 Apr 28;126(16):7346-7355. doi: 10.1021/acs.jpcc.2c01432. Epub 2022 Apr 19.
While the phenomenon of metal substrate adatom incorporation into molecular overlayers is generally believed to occur in several systems, the experimental evidence for this relies on the interpretation of scanning tunneling microscopy (STM) images, which can be ambiguous and provides no quantitative structural information. We show that surface X-ray diffraction (SXRD) uniquely provides unambiguous identification of these metal adatoms. We present the results of a detailed structural study of the Au(111)-FTCNQ system, combining surface characterization by STM, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy with quantitative experimental structural information from normal incidence X-ray standing wave (NIXSW) and SXRD, together with dispersion-corrected density functional theory (DFT) calculations. Excellent agreement is found between the NIXSW data and the DFT calculations regarding the height and conformation of the adsorbed molecule, which has a twisted geometry rather than the previously supposed inverted bowl shape. SXRD measurements provide unequivocal evidence for the presence and location of Au adatoms, while the DFT calculations show this reconstruction to be strongly energetically favored.
虽然一般认为在多个体系中都会出现金属衬底吸附原子掺入分子覆盖层的现象，但对此的实验证据依赖于扫描隧道显微镜（STM）图像的解读，而这些图像可能存在歧义，并且无法提供定量的结构信息。我们表明，表面X射线衍射（SXRD）能够唯一地明确识别这些金属吸附原子。我们展示了对Au(111)-FTCNQ体系进行详细结构研究的结果，该研究将STM表面表征、低能电子衍射和软X射线光电子能谱与来自正入射X射线驻波（NIXSW）和SXRD的定量实验结构信息相结合，同时还进行了色散校正密度泛函理论（DFT）计算。在吸附分子的高度和构象方面，NIXSW数据与DFT计算结果之间取得了极佳的一致性，该吸附分子具有扭曲的几何形状，而非先前认为的倒碗状。SXRD测量为金吸附原子的存在和位置提供了明确的证据，而DFT计算表明这种重构在能量上非常有利。
