Controllable atomic layer deposition of one-dimensional nanotubular TiO2

► One-dimensional TiO2 nanotubes were synthesized by atomic layer deposition (ALD). ► Two substrates were used in ALD-TiO2, anodic aluminum oxide (AAO) and carbon nanotubes (CNTs). ► The two routes resulted in pure TiO2 nanotube arrays and coaxial TiO2-CNT nanotubes, respectively. ► The TiO2 nanotubes could be tuned from amorphous to crystalline phase in the range 150-250 °C. ► The TiO2 nanotubes could also be controlled on their wall thickness.