Enhancement of dielectric constant in transition metal doped ZnO nanocrystals

We have presented dielectric studies on Zn1-xCoxO, Zn1-xFexO, and Zn1-xFex/2Cox/2O (x=doping level) semiconducting nanoparticles (similar to 2-40 nm). For all those samples, dielectric constant (epsilon) is found to exhibit a maximum with x. Enhancement of epsilon is found to be similar to 250 times for Zn0.85Co0.15O and similar to 400 times for Zn0.8Fe0.1Co0.1O from that of ZnO. Presence of effective higher oxidation state of transition metals ions in ZnO due to Fe/Co doping resulting in space charge polarization possibly yields this effect. The simultaneous existence of high epsilon, semiconducting, and ferromagnetic like behaviour at 300 K seems to propose Zn0.8Fe(0.1)Co(0.1)O, promising for technological application. (C) 2014 AIP Publishing LLC.