title: Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature.
abstract: Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications.
authors.affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan ; Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan.
authors.forename: Da-Ren
authors.initials: DR
authors.lastname: Hang
authors.affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan.
authors.forename: Sk Emdadul
authors.initials: SE
authors.lastname: Islam
authors.affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan.
authors.forename: Krishna Hari
authors.initials: KH
authors.lastname: Sharma
authors.affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan ; Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan.
authors.forename: Shiao-Wei
authors.initials: SW
authors.lastname: Kuo
authors.affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan.
authors.forename: Cheng-Zu
authors.initials: CZ
authors.lastname: Zhang
authors.affiliation: Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 70 Lienhai Rd., Kaohsiung 804, Taiwan.
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Wang
keywords: Annealing; Photoluminescence; Raman; Zinc oxide