Preparation and photoelectric properties of La-doped ZnO films

Among the various semiconducting metal oxide materials, ZnO films are highly attractive in the development of materials area. In order to improve the photoelectric properties of ZnO films, La-doped ZnO films were prepared by sol-gel method and the changes in conductive properties, light transmission and structure of the doped ZnO films were investigated. The research result shows that the La doping can improve the conductivity of the ZnO films, and when the La concentration increased, the resistivity first decreased and then increased, showing the "U" shaped variation. The resistivity of modified ZnO films drops to the lowest point of 1.84 Ω cm when the annealing temperature is 450 C and La³⁺ concentration is 0.35 mol%. La doping can also improve the transmittance of ZnO films. The transmittance at the visible region of films is all over 82 %, and the highest value is up to 97 %. Annealing temperature also has an important impact on the electrical conductivity of the films: the resistivity declined further to 0.92 Ω cm as annealing temperature increased to 500 C. But due to grain growth, it is not conducive to the improvement of light transmission properties.