Abstract
High resolution Scanning Auger Electron Spectroscopy (AES) is used to demonstrate the compositional variation across self-organized TiO2 nanotube layers grown in fluoride containing ethylene glycol electrolytes. The analysis results show a distinct fluoride rich layer in between the TiO2 nanotubes and particularly in the triple points of the hexagonally ordered nanotubular arrays. AES analysis further revealed that extended e-beam exposure leads to a decrease in the fluoride signal (electron beam induced decomposition of fluoride species). The proof of the existence of a fluoride rich layer located between the tube walls strongly supports fluoride dissolution as the reason for a transition from a porous to a tubular morphology. (C) 2011 Elsevier B.V. All rights reserved.