Influence of Cobalt Doping on the Physical Properties of Zn0.9Cd0.1S Nanoparticles

Zn0.9Cd0.1S nanoparticles doped with 0.005-0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration > 0.18 M, XRD pattern shows unidentified phases along with Zn0.9Cd0.1S sphalerite phase. For low cobalt concentration (a parts per thousand currency sign0.05 M) particle size, d (XRD) is similar to 3.5 nm, while for high cobalt concentration (> 0.05 M) particle size decreases abruptly (similar to 2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (similar to 3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases similar to 46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie-Weiss temperature of -75 K with antiferromagnetic coupling was obtained for the high cobalt concentration.