A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three
dimensional walls is presented. The method combines physical vapor deposition of small-molecules,
plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a postannealing
process in vacuum in order to remove the organic template. As a result, an ample variety
of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall
composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining
different semiconducting oxides and metal nanoparticles is as well explored. This method provides a
feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes
on processable substrates. The emptying mechanism and microstructure of the nanotubes have been
elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy.
In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as
photoanode in a photovoltaic cell and as a photonic oxygen gas sensorPeer reviewe