Plasmonic enhancement of UV emission from ZnO thin films induced by Al nano-concave arrays

• Published in: Applied surface science 2016-10, Vol.384, p.18-26
• Main Authors: Norek, Małgorzata, Łuka, Grzegorz, Włodarski, Maksymilian
• Format: Article
• Language: English
• Subjects: Al nano-concaves; Aluminum; Arrays; Emission; Nanostructure; Near band edge emission; Plasmonic enhancement; Plasmonics; Reflectivity spectra; Thin films; Tuning; Zinc oxide; ZnO nanostructures
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.05.029

[Display omitted] •Al nano-concave arrays with different interpore distance (Dc) were prepared.•PL of ZnO thin films deposited directly on the Al nano-concaves were studied.•The effect of 10nm Al2O3 spacer on PL emission from ZnO thin films was analyzed.•Plasmonic enhancement of the PL emission was dependent on the Dc and the spacer.•The highest 9-fold enhancement was obtained for the Al/ZnO sample with Dc ∼333nm. Surface plasmons (SPs) supported by Al nano-concave arrays with increasing interpore distance (Dc) were used to enhance the ultraviolet light emission from ZnO thin films. Two sets of samples were prepared: in the first set the thin ZnO films were deposited directly on Al nanoconcaves (the Al/ZnO samples) and in the second set a 10nm − Al2O3 spacer was placed between the textured Al and the ZnO films (the Al/Al2O3-ALD/ZnO samples). In the Al/ZnO samples the enhancement was limited by a nonradiative energy dissipation due to the Ohmic loss in the Al metal. However, for the ZnO layer deposited directly on Al nanopits synthesized at 150V (Dc=333±18nm), the largest 9-fold enhancement was obtained by achieving the best energy fit between the near band-edge (NBE) emission from ZnO and the λ(0,1) SPP resonance mode. In the Al/Al2O3-ALD/ZnO samples the amplification of the UV emission was smaller than in the Al/ZnO samples due to a big energy mismatch between the NBE emission and the λ(0,1) plasmonic mode. The results obtained in this work indicate that better tuning of the NBE − λ(0,1) SPP resonance mode coupling is possible through a proper modification of geometrical parameters in the Al/Al2O3-ALD/ZnO system such as Al nano-concave spacing and the thickness of the corresponding layer. This approach will reduce the negative influence of the non-radiative plasmonic modes and most likely will lead to further enhancement of the SP-modulated UV emission from ZnO thin films.