Optical and photocatalytic properties of oblique angle deposited $TiO2$ nanorod array

Using an oblique angle deposition technique, an array of well-aligned and tilted $TiO2$ nanorods has been fabricated by electron-beam evaporation method. The as-deposited $TiO2$ nanorod array is amorphous and porous with fibrous fine structures on the surface of individual nanorods. After annealing, the amorphous $TiO2$ crystallizes gradually into an anatase phase with annealing temperature and duration, but no visible change occurs in the porous morphology and surface fine structures even when annealed at $500°C$ for $5h$⁠. The annealing under $O2$ flow causes the optical band gap of $TiO2$ to increase from $3.32to3.39eV$⁠, due to the decrease in oxygen defect concentration. The photocatalytic activity of the annealed $TiO2$ sample is doubled compared with that of the as-deposited sample. The enhanced specific surface area by the porosity and fine structures of obliquely deposited $TiO2$ nanorod array is very promising for the applications such as chemical sensor, photovoltaic solar cell, and photocatalyst material for environmental protection.