Anodic formation of high aspect ratio, self-ordered Nb2O5 nanotubes

In the present work, we demonstrate the feasibility to form an aligned Nb2O5 nanotube layer by self-organizing anodization of Nb in a NH4F-glycerol electrolyte. In order to achieve a nanotubular rather than a nanoporous layer, careful optimization of the anodization electrolyte is required. We show that only in a narrow window of electrolyte parameters highly aligned nanotubes of 50 nm inner diameter and several micrometres in length can be formed.