Zinc sulfide is an important member of II-VI semiconductor family with a variety of applications in areas such as Electroluminescent devices, solar cells and other opto-electronic devices. Nanoparticle of Zinc sulfide exhibit physical properties different from those exhibited by bulk ZnS.
In the present project Nanoparticles of Zinc sulfide were synthesized. Controlled chemical precipitation techniques was used for the synthesis of Nanostructured samples of Zinc sulfide having the smallest grain size. Compounds of the Nanoparticles of Zinc sulfide with silver were also synthesized by wet chemical method. Three different compound samples were synthesized by varying the weight percentage of silver. X-ray diffraction technique, High resolution transmission electro microscopic studies were used to analyze the crystal structure.
The dc conductivity of compounds of Nanostructured Zinc sulfide and silver samples were measured in the temperature range 313-423K. The dc conductivity of all the compound samples was found to be higher than the dc conductivity of as prepared nanoparticle samples of Zinc sulfide. The value of dc conductivity is also found to be enhanced by four to eight orders of magnitude over that of single crystals of Zinc sulfide. This enhancement in the value of dc conductivity is explained on the basis of thermionic emission of charge carriers from the trapped states of the grain boundary potential barrier. The observed variation of dc conductivity with the difference weight percentage of silver is explained by considering the combined effects of the grain boundaries and the triple junction on the electrical transporting nanostructured Zinc sulfide.
The ac electrical properties of pellets of the compounds of nanoparticle samples of Zinc sulfide and silver were studied over a frequency range 100Hz to 3MHz at different temperatures ranging from 313 to 423K. The dielectric loss was found decrease with increase in frequency of the applied signal. Dielectric loss of all of the samples showed the same type of variation with frequency and temperature. But the dielectric losses of all the samples were found to increase with increase in temperature. The ac conductivity of the nanostructured samples of compounds of Zinc sulfide and silver were found to be strongly dependent on the frequency of the applied signal. The ac conductivity was found to vary with temperature also. The observed enhancement in ac conductivity was explained due to the increased rate of hopping of charge carriers over the green boundary barriers existing in nanostructured material.