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Migration Energy Barriers for the Surface and Bulk of Self-Assembly ZnO Nanorods

Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
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Nanomaterials 2018, 8(10), 811; https://doi.org/10.3390/nano8100811
Received: 26 September 2018 / Revised: 5 October 2018 / Accepted: 9 October 2018 / Published: 9 October 2018
(This article belongs to the Special Issue ZnO Nanorods: Synthesis, Characterization and Applications)
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Abstract

Post-annealing treatment is a necessary process to create/eliminate/repair defects in self–assembly (SA) metal oxide by providing enough thermal energy to the O atoms to overcome the migration energy barrier in ZnO. The height of migration energy barrier is dependent on the depth from the surface, which is hard to be estimated by theoretical calculations, as well as the optical analyses. SA ZnO nanorods (ZNRs) have high surface-to-volume ratio to provide complete picture between the optical and surface properties obtained by photoluminescence (PL) and ultraviolet/X-ray photoemission spectroscopy (UPS/XPS), which is used to investigate the evolution of structure and chemical states of the surface layers to reveal mutual agreement on all observations in PL, XPS, and UPS. We demonstrate variation of the surface structure of SA-ZNRs by scanning over a range of annealing temperatures and time to regulate the structure variation of SA-ZNRs, and their optical analyses agrees well with PL, XPS and UPS, which indicates the dependence of migration energy barriers on the depth from the surface of ZNR. The results reveal the well ZNRs formed at 570 °C and the further oxidation process and the formation of hydroperoxide on the Zn-rich surface of ZNRs at 640 °C. View Full-Text
Keywords: ZnO nanorods; migration energy barrier; ultraviolet photoemission spectroscopy (UPS); X-ray photoemission spectroscopy (XPS); photoluminescence (PL) ZnO nanorods; migration energy barrier; ultraviolet photoemission spectroscopy (UPS); X-ray photoemission spectroscopy (XPS); photoluminescence (PL)
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Chang, F.-M.; Wu, Z.-Z.; Huang, J.-H.; Chen, W.-T.; Brahma, S.; Lo, K.Y. Migration Energy Barriers for the Surface and Bulk of Self-Assembly ZnO Nanorods. Nanomaterials 2018, 8, 811.

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