Optical and structural properties of PbS:Bi3+ nanocrystals

We report here the growth of nanocrystalline PbS thin films by chemical bath and the effects of doping on the structural and electromagnetic properties as a function of Bi^(3+) concentration. Doping of such PbS films with Bi^(3+) produces considerable optical and structural changes that have an effect on the material properties. The morphological changes of the layers were followed by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). X-ray diffraction (XRD) spectra show growth of the zinc blende phase. The grain size for the undoped samples was found to be ~ 32 nm, whereas that for the doped samples was 25-15 nm, thus confirming AFM and SEM results. A conspicouos shift for the forbidden band gap energy was observed by optical absorption form 1.2 eV for the undoped samples to a 1.7-2.0 eV range for the doped films.