The Effect of Oxygen Pressure During Annealing on the Morphology, Structure, and Luminescence Properties of Te-Doped ZnO Thin Films

In order to understand the effect of oxygen pressure during annealing (OPA) on the morphology, structure, and luminescence properties of Te doped ZnO films, 5 wt.% Te-doped ZnO films were prepared by radio-frequency magnetron sputtering at room temperature and then annealed at 600°C under different oxygen pressure. X-ray diffraction analysis revealed that the thin film has a polycrystalline hexagonal wurtzite structure with a preferred (002) orientation. The lattice constants, dislocation density, and lattice strain of the annealed films all decreased and continued to decrease with increasing OPA. As the OPA increased, the compressive stress in the thin film weakened. Field-emission scanning electron microscopy observations revealed that the particle morphology of the as-deposited, 100 Pa annealed, and 500 Pa annealed films were willow leaf-like, irregular block-like, and willow leaf-like, respectively. The x-ray photoelectron spectroscopy analysis revealed that the proportion of V_Zn in the films gradually increased with annealing and the increase in OPA, while the proportion of Zn_i decreased. OPA is beneficial to the formation of p-type film. In the as-deposited film, Te is mainly incorporated into ZnO by substituting for Zn. After annealing in oxygen, Te predominantly substitutes for O. As the OPA increases, the tendency of Te substituting for O weakens. The photoluminescence spectra of the thin film exhibit UV-yellow emission peak around 350–600 nm and near-infrared (NIR) peaks around 820–840 nm. The intensity of the NIR peak is influenced by the annealing process and the stress state of the film.