Investigation on Optical Properties of SnSe2 Thin Films Synthesized by Two – Stage Process

Abstract

Tin diselenide (SnSe2) is a binary compound semiconductor used in wide range of opto-electronic applications. In the present study, SnSe2 thin films have been deposited by using a two – stage process that involves selenization of DC – magnetron sputtered tin metallic layers at different selenization temperatures (TS), which varied in the range, 300 - 400°C. The optical properties of SnSe2 thin films made using the optical transmittance and reflectance measurements have been investigated in detail for the first time. The optical absorption coefficient was evaluated from the transmittance versus wavelength data and was >104 cm-1 for all the samples. The band gap of the as-grown films was estimated by using the differential reflectance (dR/dλ) spectra and found to be varied in the range, 1.36 – 1.47 eV with respect to the selenization temperature. Further, the refractive index, extinction coefficient and other optical parameters such as dielectric constant, dielectric loss factor, high frequency dielectric constant and relaxation time were also determined. The electrical parameters such as conductivity, carrier concentration and carrier mobility of as-prepared layers were estimated from the optical data. From this analysis, it is inferred that the sample prepared at TS = 350°C exhibited better optical and electrical properties than the layers formed using other temperatures that are suitable for solar cell application.