Mizutani Hironori, Choi Hyeong-Kyu, Park Jinwoo, Hong Suklyun, Okada Michio
Institute for Radiation Sciences and Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
Department of Physics, Graphene Research Institute and GRI-TPC International Research Center, Sejong University, Seoul 143-747, Korea.
ACS Omega. 2023 Oct 23;8(44):41548-41557. doi: 10.1021/acsomega.3c05604. eCollection 2023 Nov 7.
We report on the covalent binding of acetonitrile (CHCN) on Si{111}-(7 × 7) at ∼300 K studied by scanning tunneling microscopy, thermal desorption spectroscopy, and first-principles theoretical calculations. The site-specific study makes it possible to unravel the site-by-site and step-by-step kinetics. A polarized CHCN prefers to adsorb on the faulted half more frequently compared to on the unfaulted half. Moreover, a molecular CHCN adsorbs four-times more preferably on the center adatom-rest atom (CEA-REA) pair than on the corner adatom-rest atom (COA-REA) pair. Such site selectivity, the number ratio of reacted-CEA/reacted-COA, depends on the number of reacted adatoms in the half-unit cell. The site selectivity and the resulting reacted-adatom patterns are understood well by considering a simple model. In this simple model, the molecular adsorption probability changes step-by-step and site-by-site with increasing reacted adatoms. Furthermore, our theoretical calculations are overall consistent with the experimental results. The site-selectivity of the adsorption of CHCN on Si{111}-(7 × 7) is explained well by the chemical reactivity depending on the local conformation, the local density of states, and the interaction between polarized adsorbates.
我们报道了通过扫描隧道显微镜、热脱附光谱和第一性原理理论计算对乙腈（CHCN）在约300 K下于Si{111}-(7×7)上的共价键合进行的研究。这种位点特异性研究使得揭示逐个位点和逐步的动力学成为可能。与未缺陷的一半相比，极化的CHCN更倾向于吸附在有缺陷的一半上。此外，分子态的CHCN吸附在中心吸附原子-静止原子（CEA-REA）对上的偏好程度是吸附在角部吸附原子-静止原子（COA-REA）对上的四倍。这种位点选择性，即反应的CEA与反应的COA的数量比，取决于半晶胞中反应的吸附原子的数量。通过考虑一个简单模型，可以很好地理解位点选择性和由此产生的反应吸附原子模式。在这个简单模型中，随着反应的吸附原子数量增加，分子吸附概率逐个位点、逐步地发生变化。此外，我们的理论计算总体上与实验结果一致。CHCN在Si{111}-(7×7)上吸附的位点选择性可以通过取决于局部构象、局部态密度以及极化吸附质之间相互作用的化学反应性得到很好的解释。
