Effect of Bi doping in tuning the structural, morphological and optoelectronic properties of solvothermally synthesized SnS nanorods

Abstract

In this work, enhanced optoelectronic properties of SnS is attained through the substitutional doping of Bi into the SnS lattice at the ‘Sn’ sites by following cost effective solvothermal method at a reaction temperature of 170 °C for a duration of 90 min. The charge states explored through XPS analysis revealed the existence of the constituent elements in Sn2+, S-Sn2+ and Bi3+ states. The chemical structure investigated through Raman analysis revealed the successful doping of Bi into orthorhombic SnS without affecting its phase purity for doping up to 12 %. With increasing the doping up to 4 %, (a) the shift in 2θ peak position to the higher angle side and the contraction in unit cell volume as evident from XRD analysis ensured the substitutional doping of Bi3+ into Sn2+ sites and (b) the direct energy band gap and electrical resistivity are reduced from 1.60 to 1.30 eV and 719×103 to 627×102 Ω cm respectively and the carrier concentration is enhanced from 1.22×1012 to 8.92×1013 cm−3 revealing the optimum doping of Bi into SnS is 4 %. Due to the effect of doping, the homogeneity in size and shape of the nanorods is enhanced with an increase in size as evident from HR-TEM analysis. The electrical transport properties obtained from Hall measurement studies showed p-type conductivity for SnS with Bi doping up to 10 %. Hence, this report provides the first experimental confirmation for the absence of any carrier polarity conversion in phase pure SnS due to the incorporation of Bi.