| Property | Value |
| Material | SnS - Tin Sulfide |
| Bulk Band Gap | Indirect 1.07 eV |
| Monolayer Band Gap | Indirect 1.45 eV |
| Crystal Structure | Orthorombic |
| Crystal Group | Pnma |
INTRODUCTION
Tin sulfide is an inorganic material from the transition metal chalcogenide series. It is p-type semiconductor with an indirect band gap, that can be modified by strain in the monolayer limit. It is suitable for optoelectronics and photovoltaics due to a large absorption coefficient and predicted high carrier mobility. Nevertheless, its layered structure produces charge carriers with relatively high effective masses. This material has been studied due to its thermoelectric, piezoelectric, anisotropic electronic and optical properties. Furthermore, SnS based devices have been developed in fields like photodetection, lithium-ion batteries, gas sensors, thermoelectric and photocatalysis. Despite this, it has a highly complex phase chemistry, and several Sn-S stoichiometric compounds are stable at room temperature, which presents a challenge for its synthesis and use.
ELECTRONIC PROPERTIES OF SNS
In bulk, SnS is a semiconductor with an indirect band gap of about 1,07 eV and orthorombic crystal structure with Pnma crystal structure symmetry. When exfoliated to a single crystal, the band structure stays indirect, with a size of 1,45 eV.
RAMAN SPECTRUM OF SNS
The Raman spectrum of SnS shows several vibrational modes related to the lattice vibrations and the vibrations of the S-S and Sn-S bonds. The spectrum typically consists of four peaks. The first peak is located at around 140 cm-1 and is associated with the Sn-S stretching mode. This peak is relatively intense and sharp, making it a useful marker for identifying SnS. The second peak is located at around 210 cm-1 and is associated with the S-S stretching mode. This peak is relatively weak and broad, making it more difficult to observe. The third peak is located at around 290 cm-1 and is associated with the Sn-Sn stretching mode. This peak is relatively weak and broad, making it difficult to observe. The fourth peak is located at around 340 cm-1 and is associated with the Sn-S bending mode. This peak is relatively intense and sharp, making it a useful marker for identifying SnS.
Phonon Dispersion of SnS
The phonon dispersion of SnS is shown above. As published in “Lattice dynamics of the tin sulphides SnS2, SnS and Sn2S3: vibrational spectra and thermal transport”, Skelton et al, 2017.
References
Towards a stoichiometric electrodeposition of SnS. Otmani et al, Applied Physics A, 2021. SnS films were grown on ITO coated glass substrates by electrochemical deposition using SnCl2 and Na2S2O3 precursors in aqueous solution, with EDTA or TEA added to slow the deposition rate and adjust the pH to 1.8, resulting in polycrystalline α-SnS films with different particle sizes and crystallographic properties depending on the complexing agent used, and with optical band gap energies that shift blue when EDTA is used and red when TEA is used.
Band-structure, optical properties, and defect physics of the photovoltaic semiconductor SnS. Vidal et al, Applied Physics Letters, 2012. SnS has an indirect 1.07 eV band gap, a minority carrier effective mass of 0.2-0.5 m0, and forms intrinsic Sn vacancy defects, making it a potential earth-abundant PV material with desirable p-type carrier concentration that can be improved by S-rich growth conditions.
Enhanced Shift Currents in Monolayer 2D GeS and SnS by Strain-Induced Band Gap Engineering. Kaner et al, ACS Omega, 2020. The effects of equibiaxial strain on the band structure and shift currents of GeS and SnS were studied using first-principles calculations, showing that compressive strain significantly reduces the band gap and leads to a phase transition from semiconductor to metal, and that compressive strain significantly increases the shift currents.