Transport studies of transition metal ion doped ZnO: Bulk and thin films

The effect of doping of transition metal ions (Fe and Co) on transport properties of ZnO has been studied in both bulk and thin films. The solubility limit of these ions have been found to be higher in thin films compared to bulk. Optical measurements reveal the presence of Fe in both 2+ and 3+ state. Co is believed to be in 2+ states. Electrical resistivity measurements show that while for bulk Fe doped ZnO samples there is a decrease in ρ (T) compared to undoped ZnO, it increases for bulk Co doped ZnO samples. However, thin film samples of both types of doped compounds show a decrease in ρ (T) compared to undoped ZnO. This difference in bulk and thin film behaviour has been explained on the basis of experimental results. © 2007 Materials Research Society.