Optical studies of doped ZnS with transition metals and undoped ZnS nanomaterials

The study of nano crystalline semi-conductor thin films is a great deal of interest among the researchers for its number of application in opto-electronic and semi-conductor devices. Thin films of ZnS nano-crystals were grown into poly-vinyl alcohol matrix by chemical route at different molar concentrations. Optical properties of both un-doped and doped with transitional elements (e.g. Fe, Mn) of ZnS nano-crystalline compounds were studied. The nano structure was characterized with the help of X-ray diffraction (XRD) and Hi- resolution Transmission Electron Microscopy (HRTEM). Surface morphology was studied with the help of Scanning Electron Microscopy (SEM). Average particle size of ZnS-Mn and ZnS-Fe were found to be 5 and 30 nm. Optical absorption studies were carried out with UV-VIS Spectrophotometer and showed a strong absorbance at wavelength 297.2 nm with a tendency towards blue shift. Peak of Photo-luminescence (PL) emission spectra was obtained at 346 nm at room temperature, Mn dependant emission was found at 580 nm whereas Fe dependant emission was found around 490 nm. These data showed successful doping, X_ray Fluorescence (XRF) studies showed larger peaks for Zn and S compared to presence of peaks of dopants Mn and Fe. PL studies also confirmed presence of dopant in the nano crystallites. Selected area electron diffraction (SAED) shows a set of four well defined rings corresponding to diffraction from different planes of the nano crystallites. HRTEM image showed a well crystalline ZnS doped with Fe.