350425.fig.002a
(a)
350425.fig.002b
(b)
350425.fig.002c
(c)
350425.fig.002d
(d)
350425.fig.002e
(e)
350425.fig.002f
(f)
Figure 2: Surface morphologies of ZnO nanorods grown at 700°C for (b) 1 min, (c) 5 min, (d) 30 min, and (e) 120 min on Sn sputter-/Ni spin coated sapphire substrates by thermal evaporation with a Zn mixture of Zn and ZnO in a weight ratio of 1 : 1. (a) SEM image of Sn sputter-/Ni spin coated bilayer catalysts after pyrolysis at 650°C for 30 min and reduction at 850°C in a Ar-5% H2 mixture gas for 30 min. (f) Photoluminescence spectra for the vertically aligned ZnO nanorods in (e). The substrates were etched by a 0.1 M NaOH solution for 15 s. The inset in (c) was enlarged from the white square-selected area.