The electronic structures and band gaps of silicene (the Si analogue of graphene) adsorbed with halogen elements are studied using the density functional theory based screened exchange local density approximation method. It is found that the band gaps of silicene adsorbed with F, Cl, Br and I have a nonmonotonic change as the periodic number of the halogen elements increases. This is attributed to the transfer of contributions to band gaps from Si-Si bonding to Si-halogen bonding.

The geometric and electronic properties of silicene paired with a MoS2 substrate are studied systematically by using density functional theory with van der Waals corrections. It is found that the nearly linear band dispersions can be preserved in the heterobilayers due to the weak interface interactions. Meanwhile, the band gap is opened because of the sublattice symmetry broken by the intrinsic interface dipole. Moreover, the band gap values could be effectively modulated under an external electric field. Therefore, a way is paved for silicene-MoS2 heterobilayers to be candidate materials for logic circuits and photonic devices.

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