Tailoring UV emission from a regular array of ZnO nanotubes by the geometrical parameters of the array and Al2O3 coating |
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Affiliation: | 1. Department of Physics, Faculty of Sciences and Arts, Bingol University, Bingol, Turkey;2. Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia;3. Department of Physics and Astronomy, College of Science, King Saud University, Riyadh, Saudi Arabia;4. Department of Physics, Faculty of Science, Firat University, Elazig 23169, Turkey |
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Abstract: | Self-aligned and equal-spaced zinc oxide (ZnO) nanotube arrays were fabricated with anodic aluminum oxide (AAO)-assisted growth and the ALD technique. The near band-edge (NBE) emission was strongly affected by the nanotube's geometrical parameters, such as a packing density and thickness of the nanotube walls. The NBE emission was further enhanced with Al2O3 coating. The effect was analyzed by X-ray photoelectron spectroscopy (XPS) and ascribed to the surface defect passivation and a ZnAl2O4 spinel formation. The NBE emission enhancement was greater in ZnO nanotubes with thicker walls. A smaller UV enhancement factor was explained by less uniform and integral Al2O3 coverage of the ZnO nanotubes with thinner walls; this, possibly induced a variation of the Al2O3 refractive index along the nanotubes. As a result, the optical conditions at the ZnO/Al2O3/air interfaces was changed and the light extraction efficiency was reduced in the latter samples. |
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Keywords: | ZnO nanotubes Anodic alumina Surface passivation Luminescence properties Atomic layer deposition |
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