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 degrees C for 5 h. The annealing under O-2 flow causes the optical band gap of TiO2 to increase from 3.32 to 3.39 eV, 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. (c) 2008 American Vacuum Society.