Xu Xun, Zhuang Jincheng, Du Yi, Feng Haifeng, Zhang Nian, Liu Chen, Lei Tao, Wang Jiaou, Spencer Michelle, Morishita Tetsuya, Wang Xiaolin, Dou Shi Xue
Institute for Superconducting and Electronic Materials (ISEM), University of Wollongong, Wollongong, NSW 2525, Australia.
Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P. R. China.
Sci Rep. 2014 Dec 18;4:7543. doi: 10.1038/srep07543.
Epitaxial silicene, which is one single layer of silicon atoms packed in a honeycomb structure, demonstrates a strong interaction with the substrate that dramatically affects its electronic structure. The role of electronic coupling in the chemical reactivity between the silicene and the substrate is still unclear so far, which is of great importance for functionalization of silicene layers. Here, we report the reconstructions and hybridized electronic structures of epitaxial 4 × 4 silicene on Ag(111), which are revealed by scanning tunneling microscopy and angle-resolved photoemission spectroscopy. The hybridization between Si and Ag results in a metallic surface state, which can gradually decay due to oxygen adsorption. X-ray photoemission spectroscopy confirms the decoupling of Si-Ag bonds after oxygen treatment as well as the relatively oxygen resistance of Ag(111) surface, in contrast to 4 × 4 silicene [with respect to Ag(111)]. First-principles calculations have confirmed the evolution of the electronic structure of silicene during oxidation. It has been verified experimentally and theoretically that the high chemical activity of 4 × 4 silicene is attributable to the Si pz state, while the Ag(111) substrate exhibits relatively inert chemical behavior.
外延硅烯是由单层硅原子以蜂窝状结构堆积而成，它与衬底表现出强烈的相互作用，这种相互作用极大地影响了其电子结构。到目前为止，电子耦合在硅烯与衬底之间化学反应性中的作用仍不清楚，而这对于硅烯层的功能化非常重要。在此，我们报道了在Ag(111)上外延生长的4×4硅烯的重构和杂化电子结构，这些是通过扫描隧道显微镜和角分辨光电子能谱揭示的。Si和Ag之间的杂化产生了一种金属表面态，该表面态会由于氧吸附而逐渐衰减。X射线光电子能谱证实了氧处理后Si-Ag键的解耦以及Ag(111)表面相对于4×4硅烯[相对于Ag(111)]具有相对的抗氧性。第一性原理计算证实了硅烯在氧化过程中电子结构的演变。实验和理论均已验证，4×4硅烯的高化学活性归因于Si pz态，而Ag(111)衬底表现出相对惰性的化学行为。
