Tuning the structural, electronic, mechanical and optical properties of silicene monolayer by chemical functionalization: A first-principles study

Commercial purposes of two-dimensional silicene are usually suppressed in nanoelectronic and optoelectronic devices by its zero-band gap. Here, the halogen atoms are detected to open the bandgap of silicene monolayer by the chemical functionalization, and comprehensive analysis of the effects of halogenation on the structural, electronic, mechanical and optical properties are conducted via first-principles calculations within the framework of density functional theory. Our simulation results prove that the halogenation makes silicene structure more distorted but maintains good stability. Specifically, Full-and Janus-functionalization endow silicene with direct bandgap ranging from 1.536 to 2.123 eV by the HSE06 functional, while half-functionalization renders silicene metallic and retains semiconducting characteristics. In the above three configurations, the bond between the halogen atom and the host Si atom is predominantly ionic and the ionicity of the former two configurations decreases as the period number of the halogen atom increases. Furthermore, the halogenated silicene monolayers exhibit a hard mechanical property and relatively strong ability to resist deformation based on calculated Young's modulus Y and Shear modulus G except for the F-Si monolayer. And the light absorption of pristine silicene monolayer is increased by halogenation in the UV-Vis light spectrum.