Influence of In Situ Oxide Dissolution on the Bottom Morphologies of Detached TiO₂ Nanotube Films

Abstract

Free-standing TiO 2 nanotube (NT) films with through holes (i.e., open bottoms) are useful for various applications. In this paper, we report the significant influence of in situ chemical etching during the detachment process on the morphological variation of TiO 2 NT bottoms. Under a high temperature detachment anodization, we noted a high detachment rate with controllable bottom morphologies. Influenced by anodization durations, the bottom opening size could be controlled with morphology transition changing from closed to partially open and then to fully open bottoms. The underlying formation mechanism of variable bottom conditions has been examined through the consideration of field-assisted chemical dissolution of both the barrier layer and the sides of the tubes at the bottom. The production of well-defined through-hole tube membranes in a reliable and controllable way is essential for their practical applications.