Fluorosilicene/chlorosilicene bilayer semiconductor with tunable electronic and optical properties

摘要

Using comprehensive density functional theory calculations, the structural, electronic, and optical properties of novel fluorosilicene/chlorosilicene (F-silicene/Cl-silicene) heterobilayer are investigated. Our results unveil that the presence of hetero-halogen bonding (Si-F--Cl-Si) has a remarkable influence on the F-silicene/Cl-silicene bilayer. The F-silicene/Cl-silicene heterostructure in the most stable pattern has a moderate band gap of 0.309 eV, lower than that of isolated halogenated silicene. Encouragingly, F-silicene/Cl-silicene heterobilayers all have a direct band gap nature, irrespective of the stacking pattern, thickness and external electric fields (E-fields), which is an advantage over MoS_2 layers. In addition, applying appropriate E-field leads to a significant enhancement of binding strength of the F-silicene/Cl-silicene heterobilayer. Especially, the band gap of the F-silicene/Cl-silicene heterobilayer can be effectively modulated by E-fields, even a semiconductor-metal transition occurs. Moreover, the interfacial hetero-halogen interaction changes the optical properties of isolated halogenated silicene; the adsorption edge of imaginary part of the dielectric function displays a corresponding redshift in comparison with that of isolated halogenated silicene, which makes the F-silicene/Cl-silicene heterostructure active over the visible range. The complete electron-hole separation also enhances the photocatalytic efficiency of the F-silicene/Cl-silicene heterobilayer. Overall, the moderate band gap, effective band gap modification by external E-field, robust direct band gap nature, suitable band edge positions, and type-II band alignment enable the F-silicene/Cl-silicene heterobilayer to have great potential applications in the field of optical and nanoelectronic devices.