Optical constants and dispersion parameters of La-doped ZnS nanocrystalline films prepared by sol-gel technique

The structure, morphology and particle size of La-doped ZnS nanocrystalline films were investigated by XRD, SEM and FTIR. XRD showed that the obtained films are nanocrystalline corresponding to the hexagonal ZnS phase with the particle size 3.44-15.13 nm. Optical properties of La-doped ZnS nanocrystalline films were investigated by UV-vis absorption technique. The band gap energy of nanocrystalline films was found to be 2.93 to 2.77 eV. Wemple - Didomenico single effective oscillator model was used to study the dispersion of nanocrystalline films refractive index. The red shift in the absorption band edge of the La-doped ZnS samples provides possibility for improving the solar energy application of ZnS.