Influence of Fe²⁺ and Ni²⁺ contents on the optical and electrical properties of ZnS quantum dots

The work reports a well controlled synthesis of un-doped and Fe²⁺ and Ni²⁺ doped ZnS quantum dots (QDs) based highly luminescent of pure cubic zinc blende structure. The samples were characterized for structural, morphological, optical and electrical parameters and great care has been made in correlating all these properties. The optimum concentrations of Zn_1−xFe_xS and Zn_1−xNi_xS dopants were found to be x = 0.2 for superior optical and electrical properties. Incorporation of Fe²⁺ or Ni²⁺ into ZnS lattice have generated acceptor level as an isolated state just above the valence band of ZnS, and hence electron requiring less excitation energy for transferring from the acceptor level to the conduction band. Moreover, it was found that the PL emission intensity of Fe²⁺ doped ZnS QDs is higher than that of Ni²⁺ doped. The results indicated that the active luminescent centers created by dopants and localized surface plasmon resonance energy transfer of ZnS QDs significantly increased with Fe²⁺ ions into the ZnS lattice. Over all in light of the results obtained during the study, the doped samples can have potential for function in vast variety of applications.