Fig. 3

SEM images of anodized TiO₂ nanotube layers by different anodization processes of Ti. a The highly ordered TiO₂ nanotubes (in top and side view) are obtained in organic electrolyte systems, with self-ordered surface dimples (right) which in fact are metallic surfaces when the tube layers are removed. Reproduced from ref. [1]. b The disordered TiO₂ nanotubes are grown in patches on the surface area and fused together to bundles in chloride containing electrolyte by an ultrafast anodization technique known as rapid-breakdown anodization (RBA). Reproduced from ref. [1] and [37]