ZnO nanowire arrays: controllable preparation and effect of annealing temperature on optical properties

Abstract

A controllable fabrication process of ZnO nanowire arrays has been investigated by a hydrothermal method. Experimental results showed that the structure and size of the as fabricated ZnO nanowire arrays can be controlled efficiently by filling ratio, concentrations of (NH₄)₂S₂O₈ and NaOH, and size of zinc foil. The large filling ratio [80% (v/v)], the low concentrations of (NH₄)₂S₂O₈ (0·095M) and NaOH (0·48M), and the small size (15×15 mm) of the Zn foil were proved to be an optimal condition to give rise to the formation of small diameter ZnO nanowire arrays (10–250 nm). Photoluminescence (PL) spectra of ZnO nanowires annealed at various temperatures displayed a near band edge emission around 380 nm and a visible emission around 435 nm originated from the electronic defect. PL spectrum of the sample annealed at 450°C revealed that the photoluminescence property of the ZnO nanowire arrays can be improved remarkably, and the corresponding Raman spectra showed the similar trend. Based on this promising fabrication technique, the growth mechanism of the ZnO nanowire arrays was also studied. This work developed a simple, clean, and effective route for fabricating large area ZnO nanowire arrays, which will be applicable to the tuning of ZnO nanodevices.

Keywords:

• ZnO nanowires
• Control preparation
• Annealing
• Optical properties

Acknowledgements

We thank Professor W. Guo, Mr K. Wang and Professor S. P. Lau for fruitful discussions. This work was supported by Jiangsu Province NSF (BK2010501), Ph.D. PFMEC (20103218120035) and Innovation Fund of NUAA (NS2012009, NS2013095).