Substrate Temperature-Dependent Physical Properties of Thermally Evaporated Sn_4Sb_6S_(13)Thin Films

In this work, the homogenous thin films of sulfosalt Sn₄Sb₆S₁₃ were successfully synthesized by the thermal evaporation technique onto corning 7059 glass substrates heated at various temperatures in the range of 30-200°C. The surface morphology and structural characteristics of Sn₄Sb₆S₁₃ films were analyzed by atomic force microscopy, X-ray diffraction, and energy-dispersive X-ray, respectively. The X-ray diffraction analysis revealed that Sn₄Sb₆S₁₃ thin films crystallized in monoclinic structure according to a preferential direction (\overline{6} 11). An improvement in the structural properties by increasing the substrate temperature was observed. The values of some important parameters such as absorption coefficient (α), band gap (E_g), refractive index (n), extinction coefficient (k), and dielectric constant (ε_∞) of thin film were determined. The absorption coefficient was larger than 10⁵ cm^-1 in the visible range. The electron transition of Sn₄Sb₆S₁₃ films was direct allowed with the values that decreased (2-1.69 eV) by increasing substrate temperature from 30 to 200°C. The dispersion data obeyed the single oscillator relation of the Wemple-DiDomenico model and Cauchy model. The electrical free carrier susceptibility and the carrier concentration of the effective mass ratio were estimated according to the model of Spitzer and Fan.