Air Annealing Effect on Oxygen Vacancy Defects in Al-doped ZnO Films Grown by High-Speed Atmospheric Atomic Layer Deposition

• Published in: Molecules (Basel, Switzerland) Switzerland), 2020-10, Vol.25 (21), p.5043
• Main Authors: Hsu, Chia-Hsun, Geng, Xin-Peng, Wu, Wan-Yu, Zhao, Ming-Jie, Zhang, Xiao-Ying, Huang, Pao-Hsun, Lien, Shui-Yang
• Format: Article
• Language: English
• Subjects: Absorptivity; Aluminum; Aluminum - chemistry; aluminum-doped zinc oxide; Annealing; atomic layer deposition; Atomic layer epitaxy; Carbon; Crystal defects; Defect annealing; Grain size; Hall effect; High speed; Membranes, Artificial; Oxygen - chemistry; oxygen vacancy; Photoelectron spectroscopy; Photoelectrons; Photovoltaic cells; Spectrum analysis; Surface Properties; Thin films; X-Ray Diffraction; Zinc oxide; Zinc Oxide - chemistry; Zinc oxides
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules25215043

In this study, aluminum-doped zinc oxide (Al:ZnO) thin films were grown by high-speed atmospheric atomic layer deposition (AALD), and the effects of air annealing on film properties are investigated. The experimental results show that the thermal annealing can significantly reduce the amount of oxygen vacancies defects as evidenced by X-ray photoelectron spectroscopy spectra due to the in-diffusion of oxygen from air to the films. As shown by X-ray diffraction, the annealing repairs the crystalline structure and releases the stress. The absorption coefficient of the films increases with the annealing temperature due to the increased density. The annealing temperature reaching 600 °C leads to relatively significant changes in grain size and band gap. From the results of band gap and Hall-effect measurements, the annealing temperature lower than 600 °C reduces the oxygen vacancies defects acting as shallow donors, while it is suspected that the annealing temperature higher than 600 °C can further remove the oxygen defects introduced mid-gap states.