Temperature dependence carrier transport behavior of transparent ZnO:Y nanocrystalline films

The Y-doped ZnO nanocrystalline films were deposited on the glass substrates by sol-gel method. X-ray diffraction measurements of the films showed the same wurtzite hexagonal structure and preferential orientation along the c-axis. The grain size of the ZnO films was decreased by the doping of Y. Temperature dependence resistivity showed a semiconductor transport behavior for the nanocrystalline films. At low temperature region, the resistivity can be fitted well with the behavior of Mott variable range hopping, σ(T)=σ_h0 exp[-(T₀/T)ⁿ] with n=1/4. On the contrary, at high temperature region, the transport mechanism can be fitted with semiconductor behavior by Arrhenius equation, σ(T)=σ₀ exp[-(E_a/kT)^m] with m=1. The activation energy E_a is increased from 0.47 meV for nondoped ZnO film to 0.83 meV for Zn_0.98Y_0.02O film obtained from equation. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the Y-doped ZnO films are affected by the doping of Y.