Sodium-doped oriented zinc oxide nanorod arrays: insights into their aqueous growth design, crystal structure, and optic
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Research Letter
Sodium-doped oriented zinc oxide nanorod arrays: insights into their aqueous growth design, crystal structure, and optical properties Amir Hassanpour, Department of Physics, Concordia University, Montreal H4B 1R6, Canada; Institut National de la Recherche Scientifique, Centre Énérgie, Matériaux, Télécommunications 1650, boulevard Lionel-Boulet, Varennes J3X 1S2, Canada; International Research Center for Renewable Energy (IRCRE), School of Energy & Power Engineering, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China Shaohua Shen, International Research Center for Renewable Energy (IRCRE), School of Energy & Power Engineering, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China Pablo Bianucci, Department of Physics, Concordia University, Montreal H4B 1R6, Canada Address all correspondence to Pablo Bianucci at [email protected] (Received 23 November 2017; accepted 13 March 2018)
Abstract Cation doping is a practical way of engineering the optical properties of one-dimensional semiconductor nanomaterials, such as their band gap. We have grown zinc oxide (ZnO) nanorods doped with sodium cations (Na+) using a hydrothermal method at temperatures as low as 60 °C. We have investigated the effect of different concentrations of Na+ on structural and optical properties and morphology of the ZnO nanostructures. We have also simulated and discussed the chemical route of formation of doped and undoped ZnO nanorods. We found that, for low-temperature hydrothermal doping of ZnO nanorods with Na+, the optimum concentration ratio of zinc to sodium precursors is 1:10.
Introduction Inorganic wide band gap materials, such as zinc oxide (ZnO), in the form of one-dimensional nanostructures have attracted a lot of attention due to their captivating electrical, magnetic and optical properties. A very significant advantage of these materials is their capability to sustain lattice excitons at room temperatures when photons are absorbed.[1] As synthesized, ZnO contains an excess of electrons because of the donor nature of its intrinsic point defects. Finding a reliable way to fabricate p-type ZnO is crucial for future optoelectronic devices. Cation doping is a common technique to reach this goal. Among all cations, sodium (Na) is one of the suitable candidates in the group I elements as a dopant to achieve stable p-type ZnO nanorods. This is because Na impurities become shallow acceptors, which can provide a large population of holes across the host lattice.[2] In theory, Na+ can incorporate into the ZnO lattice interstitially in combination with neighboring oxygen vacancies, and increase the overall number of acceptor centers in it.[3] The other significant advantage of Na doping is the improvement of photovoltaic properties of ZnO nanorods.[4] This enhancement has been attributed to fewer inherent defects in Na-doped samples in comparison to pristine ZnO. Lee et al.[5] reported an improved photoelectrochemical watersplitting photocurrent for ZnO doped with Na+. Moreover, Na+ doping c
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