Fabrication and phase characterization study of SnS thin films under controlled sulfur deposition temperature

Abstract

SnS thin films were prepared from the multilayer of Sn and S using vacuum and atmospheric (atm) pressure thermal evaporation methods respectively, followed by vacuum annealing process at 360°C for 1.5 hour. For the multilayer, sulphur layer was deposited at 175°Cand 200°C 5 hr and 250°C for 2.5hr duration from alumina crucible under standard atm condition, whereas Sn film of thickness 10nm was coated alternatively under 1E-5 mbar using thermal evaporation method. XRD studies shows that at low sulfurization temperature (Ts) of 175°C Sn and Sn2S3 is present because of the low formation energy of Sn2S3 than SnS and by increasing Ts to 200°C SnS phase is formed confirm from XRD, with decreasing the intensity of Sn peaks which indicates that this temperature could accelerate the formation of SnS phase. Raman analysis also confirms the formation SnSphase(95±2, 190±2,218±2, 164±2, 290±4 cm-1) along with Sn2S3 (58 and 307 cm-1) and Sn phases (125cm-1). Raman analysis shows that the relative intensity (RI) (%) of Sn decreases and RI (%) of SnS increases systematically by increasing Ts. Importantly, the formation of tin oxide phases is not observed under any of these conditions as confirmed by Raman and XRD analysis. The mean particle size increases from 33nm (Sn) to 97nm (SnS) after sulfurization process as corroborated by AFM. The absorbance spectra clearly indicate a significant change in the absorbance by varying Ts. A broad absorption arises due to Sn in samples S1 and S4 which disappears in S2 and S3 due to formation of SnS phase, confirmed by Raman and XRD analysis.