Influence of Post-Annealing Temperature on Properties of Ta-Doped ZnO Transparent Conductive Films

Ta-doped ZnO transparent conductive films are deposited on glass substrates by rf sputtering at 300°C. The influence of the post-annealing temperature on the structural, morphologic, electrical, and optical properties of the films is investigated by x-ray diffraction, Hall measurement, and optical transmission spectroscopy. The lowest resistivity of 3.5×10^-4Ω・cm is obtained from the film annealed at 400°C in N₂. The average optical transmittance of the films is over 90%. The optical bandgap is found to decrease with the increase of the annealing temperature.