Pressure induced structural and optical properties of cubic phase SnSe: An investigation for the infrared/mid-infrared optoelectronic devices

The narrow bandgap Tin Selenide (SnSe) is a promising material for optoelectronic, photovoltaic and thermoelectric applications. A new phase cubic π-SnSe is investigated under pressure for the first time. The studies were carried out by applying uniaxial hydrostatic pressure on π-SnSe structure from 0 GPa to 40 GPa. The results indicate that the structural parameters such as lattice parameters and cell volume show inverse relation to the pressure and shows smooth decreasing behaviour from 0 to 40 GPa. The bandgap of π-SnSe shows a significant variation at different external hydrostatic pressure (GPa). At 0 GPa its bandgap nature is direct and when pressure started to increase from 5 to 30 GPa it shows an indirect nature, and at further increase of pressure it started to exhibit the metallic behaviour (35-40 GPa). From the detailed analysis of the optical properties, it is concluded that external pressure might be the key reason to enhance the near/mid infrared light activity. The value of static dielectric constant and refractive index changes from 10.10 to 76.20 and 3.18 to 8.74 respectively as pressure increases from 0 to 40 GPa. Also, absorption energy increases as new peaks started to emerge with the increase in pressure. Moreover conduction shows substantial variation from 4.63 to 10.80 (1/fs) with pressure. The optical property enhancement is mostly due to the pressure modified electronic structures of π-SnSe (cubic phase). The tuning/manipulation of the structural and optical properties of π-SnSe suggest that this new cubic phase has a wide range of applications for pressure based optoelectronic systems.