Influence of hydrogen introduction on structure and properties of ZnO thin films during sputtering and post-annealing

Abstract ZnO thin films were prepared in Ar and Ar + H 2 atmospheres by rf magnetron sputtering, and then they were annealed in vacuum and Ar + H 2 atmosphere, respectively. The structure and optical–electrical properties of the films were investigated by X-ray diffraction, transmittance spectra, and resistivity measurement, and their dependences on deposition atmosphere, annealing treatment, and aging were studied. The results showed that adding H 2 in deposition atmosphere improved the crystallinity of the films, decreased lattice constant, increased band gap, decreased the resistivity by the order of 10 4 Ω cm, but exhibited poor conductive stability with aging. After Ar + H 2 and vacuum annealing, crystallinity of the films deposited in Ar and Ar + H 2 was further improved; their resistivity was decreased by the order of 10 5 and 10 1 Ω cm, respectively, and exhibited high conductive stability with aging. We suggest that the formed main defect is V O and H i when H 2 is introduced during deposition, which decreases the resistivity but cannot improve the conductive stability; hydrogen would remove negatively charged oxygen species near grain boundaries during Ar + H 2 annealing to decrease the resistivity, and grain boundaries are passivated by formation of a number of V O –H complex (H O ) to improve the conductive stability at the same time. Under vacuum annealing, the hydrogen that is introduced non-intentionally from deposition chamber maybe plays an important role; it exists as H O in the films to improve the conductive stability of the films.