Figure 2From: Transparent TiO2 nanotube array photoelectrodes prepared via two-step anodization Top-view SEM images of TiO 2 NT arrays prepared by (a) single-step anodization process, (b) two-step anodization process, and (c) two-step anodization process and subsequent pore-widening process, where the inset in (a) shows the top surface morphology after Ar-ion etching and the insets in (b) and (c) show the images at the same magnification. Back to article page