Li Shuang, Wu Yifeng, Tu Yi, Wang Yonghui, Jiang Tong, Liu Wei, Zhao Yonghao
Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, China.
Sci Rep. 2015 Jan 26;5:7881. doi: 10.1038/srep07881.
Defects are almost inevitable during the fabrication process, and their existence strongly affects thermodynamic and (opto)electronic properties of two-dimensional materials. Very recent experiments have provided clear evidence for the presence of larger multi-vacancies in silicene, but their structure, stability, and formation mechanism remain largely unexplored. Here, we present a detailed theoretical study of silicene monolayer containing three types of defects: vacancy clusters, extended line defects (ELDs), and di-adatoms. First-principles calculations, along with ab initio molecular dynamics simulations, revealed the coalescence tendency of small defects and formation of highly stable vacancy clusters. The 5|8|5 ELD - the most favorable extended defect in both graphene and silicene sheets - is found to be easier to form in the latter case due to the mixed sp(2)/sp(3) hybridization of silicon. In addition, hybrid functional calculations that contain part of the Hatree-Fock exchange energy demonstrated that the introduction of single and double silicon adatoms significantly enhances the stability of the system, and provides an effective approach on tuning the magnetic moment and band gap of silicene.
在制造过程中缺陷几乎不可避免，且它们的存在会强烈影响二维材料的热力学和（光）电子性质。最近的实验已为硅烯中存在更大的多空位提供了明确证据，但其结构、稳定性和形成机制在很大程度上仍未得到探索。在此，我们对包含三种类型缺陷的硅烯单层进行了详细的理论研究：空位团簇、扩展线缺陷（ELDs）和双吸附原子。第一性原理计算以及从头算分子动力学模拟揭示了小缺陷的合并趋势以及高度稳定的空位团簇的形成。5|8|5 ELD——石墨烯和硅烯片中最有利的扩展缺陷——被发现由于硅的混合sp(2)/sp(3)杂化，在后一种情况下更容易形成。此外，包含部分哈特里 - 福克交换能的杂化泛函计算表明，单硅和双硅吸附原子的引入显著增强了系统的稳定性，并提供了一种调节硅烯磁矩和带隙的有效方法。
