Optical characterization of mechanically alloyed PbSnS3 nanocrystals

The present study explains the preparation of PbSnS3 nanocrystals using mechanical alloying as the processing technique and elemental powders as the starting material. The elemental powders of Pb, Sn and sublimed sulphur (S) were mechanically alloyed for 40 h. Phases evolved during mechanical alloying are explored by X-ray diffraction (XRD). The morphology and microstructural features have been investigated using High-resolution Transmission Electron Microscopy (HRTEM). UV-Vis-NIR spectroscopy has been used to measure the optical absorption characteristics. The mechanically alloyed powders show particle sizes in the range of 3-12 nm. The absorption edge extends from 503 nm to the visible region to 1360 nm near infrared region with a sudden change in slope at 860 nm, indicating the feature of indirect band gap semiconductors. The intersection point with the x-axis of extrapolating (αE)2 line as a function of E gives a direct band gap of 1.33 eV and an indirect gap of 0.59 eV.