Structural, electronic and optical properties of fluorinated bilayer silicene

Silicon (Si) is undoubtedly an excellent material for electronic applications. However, Si is not a suitable material for optoelectronic applications due to its indirect bandgap. Based on the first principles approach, we have studied different stacking (AA and AB) patterns in bilayer silicene. The phonon band structure of AA and AB-stacked "bilayer silicene" reveals that only AB-stacked silicene is stable. Different fluorinated configurations (1F, 2F, 3F and 4F) of AB-stacked bilayer silicene are analyzed in terms of structural parameters and the phonon band structure. Of the four fluorinated configurations, 2F-AB-stacked bilayer silicene has a direct bandgap of 1.23 eV. The direct bandgap allows the carriers to transit from the "valence band" to the "conduction band" with a low probability of phonon generation. Meanwhile, the other configurations either lack stability or have a zero bandgap. The proposed fluorinated bilayer silicene, in addition to having an expected integration with silicon technology, could also be suitable for visible and near-infrared light detection applications.