COMPUTER SIMULATION OF ENERGETIC BANDS AND OPTICAL PARAMETERS OF TIN DICHALCOGENIDES

Abstract

The band structure and optical properties of the bulk and one monolayer of SnS2, SnSe2, and SnTe2 were established by means of ab initio theoretical modeling. The first two bulk compounds were found to be indirect gap semiconductors, while SnTe2 behaves like a gapless semiconductor. As the atomic number of chalcogen is increased, the compounds considered show an increase in lattice constants and interatomic distances, as well as a decrease in the band gap from 2.4 to 0 eV. Upon transition from the bulk material to a single monolayer, the structural parameters remain practically unchanged. There is a proportional increase in the energy gap, whereby SnTe2 becomes a narrow-gap semiconductor with a band gap of 0.17 eV. The most interesting compound according to a practical use is tin diselenide SnSe2 due to the band gap (1.0–1.5 eV) and the absorption coefficient near the absorption edge more than 105 cm‑1 that are appropriate for photovoltaics. Ternary tin dichalcogenides are also of great interest as the variation of the chemical composition of the latter allows modifying the electronic structure and the optical properties in a wide range.