Fabrication of TiO2 nanotube on silicon substrate by two-step anodic oxidation for wafer level supercapacitors application

In this paper, TiO₂ nanotube arrays were tried to be fabricated on SiO₂/Si substrates by using "ultra weak" anodic oxidation with two-step method. We investigated the influence of key parameters on the structure of the TiO₂ nanotubes including potential, electrolyte and the oxidation time applied in two-step method. It is found that the morphology of the oxidized TiO₂ nanotube arrays was strongly affected by the oxidation conditions. In the experiment, the titanium film with thickness of 400 nm was firstly sputtered on SiO₂/Si substrates, and then low potentials of 10 V for 20 sec and 0.5 V for 25 min were respectively applied in HF solution with the low concentration of 0.05 wt%. The experimental results show that the dense TiO₂ nanotubes with diameters ranged from about 90 to 270 nm with an average value of 150 nm were obtained in the two-step anodic oxidation method. The obtained TiO₂ nanotubes with higher diameters are promising for manufacturing the micro supercapacitor with high specific surface area.

I. Introduction

Titanium dioxide (TiO₂) nanotubes, as one of the nanoporous materials, have received a great deal of attention owing to its large surface area and ordered structures in recent years. It is widely used in the field of electronics, optics, catalysis and energy storage/conversion [1]. In particular, the Ti_O2 nanostructures may be used as a template (for the deposition of other materials into tubes) in analogy to aluminum and may find application for the production of magnetic recording media [2], functional electrodes and waveguides [3], or three dimensional MEMS supercapacitors [4].