Conductivity Switching of N-Doped Ta Oxide Nanotubular Arrays

By Abhayawardhana, Anusha D. & Birss, Viola I.
Published in The Journal of Physical Chemistry C NULL 2015

Abstract

Ta oxynitride (TaO?Ny) nanotubes (NTs) were synthesized by the anodization of Ta in an aqueous H?SO? + HF solution, forming Ta oxide NTs, followed by the high-temperature conversion of Ta oxide to TaO?Ny in ammonia. The electrochemical behavior of these nanotubular arrays was then investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealing a wide range of interesting properties. The Ta oxynitride NTs, which are shown to contain evenly spaced holes along their length, undergo a reversible redox process involving cation intercalation in both aqueous solutions and dry acetonitrile at potentials negative of 0.5 V, while above this, the nanotubular array is nonconducting. From the CV charges, it is possible that this reaction occurs only on the exposed TaO?Ny NT surfaces, although the nanotubular array does undergo conductivity and color switching. EIS analysis has confirmed the pseudocapacitive properties of the TaO?Ny NTs at < 0.5 V, while at potentials above this, Mott-Schottky analysis shows that they are n-type semiconductors having a donor density of ca. 6 × 1021 cm-3.

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