Structural analysis, electronic and optical properties of the synthesized Sb2S3 nanowires with small band gap

Abstract

We report a simple colloidal synthesis of two types of Sb2S 3 nanowires with small band gap and high aspect ratio. Field-emission scanning electron and transmission electron microscopies confirmed formation of high aspect ratio Sb2S3 nanowires, separated in the form of bundles and coalesced with each other in long bars. Diffuse reflectance and absorption spectroscopies revealed that the optical band-gap energies of the synthesized nanowires separated in the form of bundles are 1.56 and 1.59 eV, and coalesced with each other in long bars are 1.36 and 1.28 eV, respectively. The structure refinement showed that Sb2S3 powders belong to the orthorhombic structure with space group Pnma (no. 62). It was found that Sb2S3 nanowires separated in the form of bundles predominantly grow along the [0 1 0] direction being in the needle-like shape. The nanowires coalesced with each other in long bars rise in the form of long bars, are ribbon-like in shape and have expressed {1 0 1} facets which grow along the [0 1 0] direction. No peaks in photoluminescence spectra were observed in the spectral range from 250 to 600 nm. In order to shed more light on the experimental results concerning the band-gap energies and, in the literature generally poorly investigated electronic properties of the synthesized material, we performed theoretical calculations of the electronic structure and optical properties of the Sb2S3 samples synthesized here. This was done on the basis of density functional theory with the generalized gradient approximation, and also with an improved version of the exchange potential suggested recently by Tran and Blaha. The main characteristic is the significant improvement of the band gap value.