First-principles study of the effect of S-atom doping on the optoelectronic properties of stanene.

Context: Based on the first principles, the influence of S-atom doping on the electronic and optical properties of stanene is comprehensively examined in this work. The results show that pure stanene is a quasi-metal with zero bandgap. After doping with an S atom, opening the bandgap of pure stanene becomes possible and the state of the stanene is converted from quasi-metal to semiconductor. Analysis of the density of states reveals that the density of states of all doped systems is primarily made of the p-orbital of the Sn. The overlap population analysis showed that charge transfer occurs between S and Sn atoms under different doping concentrations. The charge transfer increases with increasing doping concentration. The charge transfer reaches a maximum at a doping concentration of 9.38%. The increase in doping concentration causes blue-shifting of the absorption and reflection peaks of the doped system as compared to those of pure stanene. It is expected that these studies can provide theoretical guidance for the practical application of stanene in optoelectronic devices.

Methods: All simulations are undertaken with the Cambridge Sequential Total Energy Package (CASTEP) (Wei et al. Physica B: Condensed Matter 545:99, 2018; Bafekry et al. Phys Chem Chem Phys, 2021; Zala et al. Appl Surf Sci, 2022; Bafekry et al. Nanotechnology, 2021; Bafekry et al. Phys Chem Chem Phys, 2021; Bafekry et al. J Phys: Condens Matter, 2021), which is based on density functional theory (DFT). For the exchange correlation, the generalized gradient approximation (GGA) is implemented with the Perdew-Burke-Ernzerhof (PBE) functional Perdew et al. Phys Rev B Condens Matter 48:4978, 1993. Using the Monkhorst-Pack technique, a specific K-point sample of the Brillouin zone was carried out Monkhorst and Pack Phys Rev B 13:5188, 1976. After the convergence tests, the K-point grid was set to 3 × 3 × 1. The plane-wave truncation energy was set to 400 eV. The residual stress for all atoms was 0.03 eV/Å. The energy convergence criterion was 1.0 × 10 eV. To prevent recurring interactions between the layers, a vacuum layer with a thickness of 20 Å was established in the Z-direction.