Vertically oriented titania nanotubes prepared by anodic oxidation on Si substrates

Vertically oriented titania nanotube arrays were fabricated by anodization of titanium film deposited on silicon substrates under different processing conditions. The anodic formation of nanoporous titania on silicon substrate was investigated in aqueous solutions mixed with highly corrosive Na2SO4/NaF/citric acid. In the result of the anodization of titanium film deposited at room temperature, a very thin layer of similar to 70 nm having a worm-like structure was grown on the top of the porous layer. But, in the case of titanium film deposited at 500 degrees, vertically oriented TiO2 nanotube arrays were formed. The average tube outer diameter of the nanotube was 74 mu to 100 run. The longest nanotube of 681 mu m was obtained at 15 V and 30 min. The current density transient curve recorded during anodization under a constant voltage showed a typical behavior for self-organized pore formation.