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Open AccessArticle

Orange/Red Photoluminescence Enhancement Upon SF6 Plasma Treatment of Vertically Aligned ZnO Nanorods

1
Laboratoire Interdisciplinaire de Spectroscopie Electronique (LISE), Namur Institute of Structured Matter (NISM), University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
2
Center of Excellence for Research in Engineering Materials, Deanship of Scientific Research, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
3
National Institute for Laser, Plasma and Radiation Physics, Magurele, P.O. Box MG-16, 077125 Bucharest, Romania
4
School of Chemical and Materials Engineering, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan
5
Department of Mechanical Engineering, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
*
Author to whom correspondence should be addressed.
Nanomaterials 2019, 9(5), 794; https://doi.org/10.3390/nano9050794
Received: 11 April 2019 / Revised: 13 May 2019 / Accepted: 20 May 2019 / Published: 23 May 2019
Although the origin and possible mechanisms for green and yellow emission from different zinc oxide (ZnO) forms have been extensively investigated, the same for red/orange PL emission from ZnO nanorods (nR) remains largely unaddressed. In this work, vertically aligned zinc oxide nanorods arrays (ZnO nR) were produced using hydrothermal process followed by plasma treatment in argon/sulfur hexafluoride (Ar/SF6) gas mixture for different time. The annealed samples were highly crystalline with ~45 nm crystallite size, (002) preferred orientation, and a relatively low strain value of 1.45 × 10−3, as determined from X-ray diffraction pattern. As compared to as-deposited ZnO nR, the plasma treatment under certain conditions demonstrated enhancement in the room temperature photoluminescence (PL) emission intensity, in the visible orange/red spectral regime, by a factor of 2. The PL intensity enhancement induced by SF6 plasma treatment may be attributed to surface chemistry modification as confirmed by X-ray photoelectron spectroscopy (XPS) studies. Several factors including presence of hydroxyl group on the ZnO surface, increased oxygen level in the ZnO lattice (OL), generation of F–OH and F–Zn bonds and passivation of surface states and bulk defects are considered to be active towards red/orange emission in the PL spectrum. The PL spectra were deconvoluted into component Gaussian sub-peaks representing transitions from conduction-band minimum (CBM) to oxygen interstitials (Oi) and CBM to oxygen vacancies (VO) with corresponding photon energies of 2.21 and 1.90 eV, respectively. The optimum plasma treatment route for ZnO nanostructures with resulting enhancement in the PL emission offers strong potential for photonic applications such as visible wavelength phosphors. View Full-Text
Keywords: ZnO nanorods; photoluminescence; SF6 plasma; visible emission; red emission ZnO nanorods; photoluminescence; SF6 plasma; visible emission; red emission
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MDPI and ACS Style

Achour, A.; Islam, M.; Vizireanu, S.; Ahmad, I.; Akram, M.A.; Saeed, K.; Dinescu, G.; Pireaux, J.-J. Orange/Red Photoluminescence Enhancement Upon SF6 Plasma Treatment of Vertically Aligned ZnO Nanorods. Nanomaterials 2019, 9, 794.

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