Development of SnS0.4Se0.6 Ternary Alloy on Annealing of Thermally Deposited Films

Abstract

The effect of annealing temperature on the evolution of different phases and morphological changes of thermally evaporated SnS1−xSex thin films was investigated. Thermal evaporation of Sn, S and Se constituent elements was performed under vacuum pressure ∼ 2 × 10−6 mbar in a vacuum coating unit (VCU) at room temperature. Annealing of the samples was carried out at a base vacuum pressure ∼ 1 × 10−3 mbar in a tubular furnace. Composition of the annealed samples was established as SnS0.4Se0.6 on the basis of energy dispersive x-ray analysis (EDAX). The films acquired alloy formation of SnS0.4Se0.6 with Sn at 473 K; SnS at 523 K; SnS and SnSe at 573 K; and SnSe at 623 K, respectively. The evolutions of the mixed phases of SnS0.4Se0.6 along with Sn, SnS or SnSe phases at different annealing temperatures were confirmed on the basis of x-ray diffraction (XRD). Moreover, the alterations in the morphological patterns of scanning electron microscopy (SEM) and variations in the parameters of Vis-NIR spectroscopic analysis corroborate to the results of x-ray diffraction (XRD). As the annealing temperature increased from 473 K to 623 K, a shift was observed in the peaks of different phases of SnS0.4Se0.6, causing variations in the unit cell parameters of constituent materials. Further, there was an improvement in the stoichiometry values of the constituent elements at higher annealing temperatures. The optical bandgap (Eg) values of SnS0.4Se0.6 films vary from 1.25 eV to 1.01 eV while absorption coefficient (α) values are ≥ 104 cm−1 for all annealing temperatures (i.e. 473–623 K), thereby making these materials, suitable candidates for the solar cell structures.