Electronic structures of silicene fluoride and hydride

Silicene is the graphene-like silicon nanosheet, which has been synthesized very recently [B. Lalmi, H. Oughaddou, H. Enriquez, A. Kara, S. Vizzini, B. Ealet, and B. Aufray, Appl. Phys. Lett. 97 , 223109 (2010)]. Using first-principles calculations, we systematically investigate the structures and properties of fluorinated and hydrogenated silicene, the silicon analogues of graphane. Different from the carbon-counterpart, the fluorination prefers the conformation with a zigzag-line buckling, while the hydrogenation keeps the chair conformation similar to graphane. A direct band gap is opened in the silicene fluoride, and the gap values can be continuously modulated by the strain. While for the hydride, a strain-induced indirect-to-direct band gap transition is found.