Effect of Fe doping on the microstructure and electrical properties of transparent ZnO nanocrystalline films

The transparent ZnO and Zn0.96Fe0.04O nanocrystalline films were deposited on the glass substrates by sol–gel method followed by repaid thermal annealing treatment. The grain size of the ZnO films was decreased by the doping of Fe. X-ray diffraction measurements of the films showed the same wurtzite hexagonal structure and preferential orientation along the c-axis. Temperature dependence resistivity showed a semiconductor transport behavior for both compositions. At high temperature region, the transport mechanism can be fitted with semiconductor behavior by Arrhenius equation, σ(T) = σ0 exp[−(Ea/kT)m] with m = 1. The activation energy Ea is increased from 0.47 meV for pure ZnO film to 0.69 meV for Zn0.96Fe0.04O film obtained from equation. At low temperature region, the resistivity can be fitted well with the behavior of Mott variable range hopping, σ(T) = σh0 exp[−(T0/T)n] with n = 1/4. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the Zn1 − xFexO films are affected by the doping of Fe in the Zn1 − xFexO films.