Structural, morphological and optical properties of the sulfosalt material SnSb4S7 thin films

Abstract

In this paper, we report the effect of the substrate temperature on the structural, morphological and optical properties of SnSb4S7 thin films elaborated by thermal evaporation at different substrate temperatures. Spectroscopic techniques like X-ray diffraction (XRD), energy dispersive X-ray (EDX), Raman spectroscopy, Atomic Force Microscopy (AFM) and UV–vis spectroscopy were used to characterize the SnSb4S7 powder and films. The X-ray diffraction analysis revealed that the powder crystallized in monoclinic structure with a preferred orientation along (2¯13¯) plane. The calculated lattice parameters were a=11.51Å, b=4.17Å, c=13.96Å and β=105.41°. SnSb4S7 thin films are polycrystalline in nature and the average grain size increases by increasing the substrate temperature. The Raman spectroscopy shows that the Raman modes for the SnSb4S7 thin films are observed at 105, 117, 140, 150, 250, 187, 303, 371, 400 and 450cm−1. Atomic Force Microscopy images revealed that the surface roughness of the films decreased from 2.37nm to 0.785nm by increasing the substrate temperature. The optical constants of the evaporated films were determined, in the spectral range 300–1800nm, from the analysis of the transmission and the reflection data. The energy band gap values decreased from 1.77eV to 1.69eV with the increase of the substrate temperature. The most significant result of the present study is that the substrate temperature can be used to modify the structural, morphological and optical properties of SnSb4S7 thin films.