Synthesis and characterization of copper and silver doped zinc sulphide nanocrystallies

Abstract

Zinc Sulphide (ZnS), Copper doped Zinc Sulphide (ZnS:Cu) and Silver)doped Zinc Sulphide nanocrystallites (ZnS:Ag) of average size 4 nm, 3 nm and 8 nm respectively, have been synthesized by chemical precipitation method and characterized. The structural and morphological studies using X)ray and high resolution transmission electron microscopy (HRTEM) measurements have confirmed hexagonal structure for the samples. The average size of the ZnS, ZnS:Cu and ZnS:Ag nanocrystallites and their d)spacing values obtained by powder XRD studies are also compared with the corresponding sizes obtained from HRTEM measurements and a very good agreement between them is obtained. Using impedance spectroscopy, the effect of grain interior and grain boundary regions on their conductivity have been studied at various temperatures for the undoped ZnS, copper doped ZnS, and silver doped ZnS nanocrystallites. Further, the results of the activation energies of the charge carriers in both the grain)interior and grain)boundary regions are found to be 1.71 eV, 3.64 eV for zinc sulphide ZnS and 1.19 eV, 1.32 eV for copper )doped ZnS (ZnS:Cu) and 1.89 eV, 3.85 eV for silver)doped zinc sulphide ZnS:Ag nanocrystallites. The conduction mechanism of undoped ZnS, copper doped ZnS, silver doped ZnS nanocrystallites have been studied at various temperatures and the results are reported. The effects of temperature and frequency on the dielectric behavior have been studied for zinc sulphide (ZnS), copper doped zinc sulphide (ZnS:Cu) and silver doped zinc sulphide (ZnS:Ag) nanocrystallites. Variations of dielectric constant as a function of frequency as the range (1 Hz) 1 MHz) and the temperature as the range (350 o C ) 600 o C) have also been studied and found that these values decrease sharply as the frequency is increased. Energy gap of the undoped ZnS, copper)doped ZnS, and silver) doped ZnS nanocrystallites have been found using Arrhenius plot. Their values are found to be 4.05 eV, 4.46 eV, and 3.87 eV respectively.