Annealing study of titanium oxide nanotube arrays

► We have studied titanium dioxide nanotube arrays by anodization of titanium foil. ► Anatase (1 0 1) only appeared on the walls of the nanotube. ► Increasing annealing temperature decreases atomic concentration of fluoride and Ti/O ratio. ► On annealing, vacancy defects diffuse toward the surface and can even heal. ► The fluoride may form vacancy complexes on the surface.