Structural, electronic, and optical properties of hydrogenated few-layer silicene: Size and stacking effects

Abstract

The size and stacking effects on the structural, electronic, and optical properties of hydrogenated few-layer silicenes (HFLSs) are investigated systematically by the first-principle calculations within density functional theory. It is found that both the formation energies and band gaps of HFLSs increases with the reduction of layer thickness. The high formation energies imply the relatively lower structural stability in the thinner HFLSs due to their high surface/volume ratio. With the reduction of layer thickness, the increasing band gaps lead to an obvious blue shift of optical absorption edge in the HFLSs. Among three different stacking HFLSs with the same thickness, the ABC-stacking one has the lowest formation energy and the largest band gap due to the strong interactions of Si layers. Moreover, the structural transition of HFLSs from the ABC-stacking sequence to the AA-stacking one will cause a relative red shift of optical absorption peaks. The results indicate that the electronic and optical properties of HFLSs strongly depend on their size and stacking modes.