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Geometric and Electronic Structures as well as Thermodynamic Stability of Hexyl-Modified Silicon Nanosheet

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journal contribution
posted on 19.02.2016, 04:55 by Feng Li, Ruifeng Lu, Qiushi Yao, Erjun Kan, Yuzhen Liu, Haiping Wu, Yongbo Yuan, Chuanyun Xiao, Kaiming Deng
The successful synthesis and outstanding properties of graphene have promoted strong interest in studying hypothetical graphene-like silicon sheet (silicene). Very recently, 2D silicon nanosheet (Si-NS) stabilized by hexyl groups was reported in experiment. We here present an atomic-level investigation of the geometric stability and electronic properties of Si-NS by density functional calculations and molecular dynamics simulations. The most stable structure of the hexyl-modified Si-NS corresponds to the one in which the hexyl groups are regularly attached to both sides of the sheet, with the periodicity of the hexyl groups on the sheet being 7.17 Å, in good agreement with the experimental value of 7.1 Å. The electrostatic repulsion effect of the hexyl groups could be an important reason for the favorable structure. The electronic structure of the hexyl-modified Si-NS shows a direct band gap that is not sensitive to the length of the alkyl group but sensitive to the strain effect, which can be used to tune the gap continuously within the whole strain range we considered. Finally, both the first-principles and the force-field-based molecular dynamics simulations show that the most stable structure of the hexyl-modified Si-NS could maintain its geometric configuration up to 1000 K.