Synthesis, characterization and chemical stability of silicon dichalcogenides, Si(SexS1−x)2

Silicon dichalcogenides have an intriguing crystal structure consisting of long tetrahedral chains held together by van der Waals forces but the electronic and optical properties have been less explored. In the present work, bulk SiSe2, SiS2, and Si(SexS1−x)2 were synthesized by the congruent melt growth method and characterized by Raman spectroscopy, X-ray Diffraction and UV/visible/IR transmission measurements supported by first-principles calculations. First-principles calculations reveal a nearly linear decrease of band gap energy in Si(SexS1−x)2 with increasing Se content, i.e., from SiS2 to SiSe2 which corresponds with a blue-shift in the transmission spectra from bulk SiSe2 to Si(Se0.6S0.4)2, and to SiS2. Air stability tests demonstrate the formation of toxic H2Se/H2S gas from sample oxidation at room temperature upon exposure to ambient air, and great care should be paid when handling these materials.