On wafer TiO2 nanotube-layer formation by anodization of Ti-films on Si

In this work, we present the self-organized formation of anodic TiO2 nanotubular layers on flat and thin sputter-deposited layers of titanium on silicon. The TiO2 nanotubes were grown by anodization of these substrates in HF/H2SO4 electrolytes at different potentials between 5 V and 20 V resulting in tubes with diameter ranging from 30 to 100 nm. The key to achieve an ordered layer from the thin film samples is to operate at low temperatures. This results in a conversion efficiency of Ti to TiO2 nanotubes close to 100% and prevents loss of large amounts of the tubes due to chemical dissolution.