Absorption and Mid-IR SHG in Two-Dimensional Halogen and Hydrogen Saturated Silicene Series

Developing nonlinear optical nanodevices compatible for the current silicon chip industry is of great interest. Modified silicene, with its single atomic silicon thickness, has become a rising material. Here, on the basis of first-principle calculations, two-dimensional halogen and hydrogen saturated silicene are proposed to be competing candidates for strong second-harmonic generation (SHG) material workings in the mid-IR range. The SHG coefficient is more than 10 times larger than KH₂PO₄ (KDP) with high electron cloud deformability around halogen atoms. Also the Si-H absorption peak is within the range of 2102-2140 cm^-1 (4673-4757 nm), red-shifted compared to 3300 cm^-1 (3030 nm) of C-H in graphane. In addition, the two-dimensional material construction method can be extended to other novel two-dimensional single-element materials, including borophene, phosphorene, germanene, arsenene, antimonene, and bismuthene.