Structural, Optical and Electrical Properties of Eu-doped CuS Nanoparticles Synthesized Through the Aqueous Route

Abstract

Eu-doped CuS nanoparticles stabilized by L-cysteine were synthesized by a low-temperature soft aqueous route. X-Ray Diffraction (XRD) patterns of the synthesized products reveal the formation of the hexagonal structure of covellite CuS. Scanning Electron Microscopy (SEM) images depict that the as-prepared nanoparticles exhibit relatively sphere like shaped morphology. Transmission Electron Microscopy (TEM) analyses show that the average size of the nanoparticles was found to be reduced with increasing the Eu concentration. UV-Visible optical absorption measurements reveal that the optical band gap is increased with increasing the Eu concentration, showing the presence of a blue shift due to quantum size effects. Impedance spectra were well modelled by introducing an electrical equivalent circuit. The electrical conductivity was found to be increased with increasing the Eu concentration. The temperature dependence of the DC conductivity confirmed the semiconducting nature of the as-prepared nanoparticles and was found to obey the Arrhenius law with two activation energies. The frequency dependence of the AC conductivity has been analyzed by Jonscher’s power law suggesting the non-overlapping small polaron tunneling (NSPT) type of conduction. The polaron hopping energy was found to be increased with increasing the Eu concentration. The dielectric constant of the as-synthesized nanoparticles was found to be decreased with the increase in Eu concentration. The dielectric loss tangent was found to be decreased and then increased at higher frequencies with increasing the Eu concentration.