Rutile phase n- and p-type anodic titania nanotube arrays with square-shaped pore morphologies

Abstract

Rutile-phase TiO2 nanotube arrays without broken walls were formed by annealing of anodically formed nanotubes in a propane flame at 650°C and in air at 750°C. An unusual morphological transformation was observed from the ellipsoidal pore-shapes of titania nanotubes grown in aqueous electrolyte to a square-shaped pore structure subsequent to the anneals. 750°C annealed nanotubes were found to be lightly p-type, rare in TiO2.