Modulation of optical properties and defects of ZnO films with preferred orientations by annealing in different atmospheres.

ABSTRACT

Nonpolar (100), polar (002), semipolar (101), and nonpolar (110) preferred oriented ZnO films were synthesized by regulated growth using the chemical bath deposition method. The crystallinity, surface morphology, and optical properties of ZnO films with different preferred orientations after annealing in different atmospheres were systematically investigated. The experimental results show an increase in crystallinity and a decrease in surface roughness of the films after annealing; in particular, the optical transmittance of semipolar (101) preferred oriented ZnO films was significantly higher than that of the other samples. XPS and PL spectra confirmed that annealing in argon effectively increased donor defects, whereas annealing in oxygen and ozone reduced donor defects in the films, and that ozone annealing was best suited to enhance acceptor defects in nonpolar (110) preferred oriented ZnO films. Argon annealing is the best for the enhancement of donor defects in polar (002) preferred oriented ZnO films. This work achieves modulation of optical properties and defects of ZnO films by annealing in different atmospheres, which provides new ideas for the application of ZnO materials.