Excellent response to near ultraviolet light and large intervalley scatterings of electrons in 2D SnS ₂

Tin disulfide (SnS₂) has attracted much attention as a novel two dimensional material due to its potential applications in electronics and optoelectronics. In this work, we investigated the optical properties of ultra-thin SnS₂ film samples (∼8 nm) via spectroscopic ellipsometry, and found that SnS₂ maintains a relatively high imaginary part of the dielectric constant (ε₂) in the range of 256-377 nm indicating high optical response. The carrier transport properties of SnS₂ were investigated considering full mode-resolved electron-phonon couplings, which reveal that the intervalley scatterings between degenerate valley (peaks) states via the fifth optical branch phonons play a dominant role in electron scattering, while ZA phonons dominate the hole scattering. The calculated electron mobility is ∼50 cm² V^-1 s^-1 which is close to previously reported experimental results. By considering full el-ph interactions based on the rigid-band approximation, the maximum value of the thermoelectric figure of merit zT reaches 0.43 at 700 K. Our work not only reveals the promising applications of SnS₂ in the fields of electronics and optoelectronics, but also showcases the computational framework for precise calculations of thermoelectric performances.