Effect of postdeposition oxidation and subsequent reduction annealing on electric and optical properties of amorphous ZnO-SnO_2 transparent conducting films

摘要

Amorphous ZnO-Sn O_2 (ZTO) films were radio frequency-magnetron sputtered on glass substrates at room temperature in pure Ar. Postdeposition oxidation and subsequent forming gas reduction annealing (O_2 FG) at 450°C increased electron concentration, mobility, and transmittance of the amorphous ZTO films simultaneously. Neither forming-gas nor oxidizing annealing alone produced the same results. Based on X-ray photoelectron spectroscopy, the second stage forming-gas annealing in O_2 FG possessed the function of reducing Zn2+ to Zn and oxidizing Sn2+ to Sn4+ simultaneously. The reduction of Zn2+ to Zn enhanced the electrical conductivity of ZTO films, while the oxidization of Sn2+ to Sn4+ resulted in improved transmittances.