Tunable dielectric constant with transition metals doping in Zn1−x(MnTM)xO (TM = Co, Fe) nanocrystals

We have presented dielectric studies on Zn1−xMnx/2Fex/2O and Zn1−xMnx/2Cox/2O (x = doping level) semiconducting nanoparticles (∼2-40 nm). Structural analyses show the formation of single phase nanoparticles. Dielectric constant (ε) is found to exhibit sensitive modulation, both with the variation of doping element (Fe and Co) and doping level (x) in ZnMnO matrix and also with frequency (f). Enhancement of ε is found to be ∼1500 times for Zn0.9Mn0.05Fe0.05O and ∼2 times for Zn0.9Mn0.05Co0.05O from that of Zn0.9Mn0.1O nanoparticles at low frequency region. The enhancement in ε can be explained on the basis of dielectric polarization, caused by the presence of different abundance of higher oxidation states of Fe and Co ions in ZnMnFeO and ZnMnCoO samples. From our observation one can choose the suitable doping element, along with suitable dopant concentration to achieve the desired higher value of ε in transition metal doped ZnMnO nanoparticles at room temperature. We have also estimated semiconducting band gap of those nanoparticles using recorded absorbance spectra.