The effect of Ti/TiO2 treatment on morphology, phase composition and semiconductor properties

Naked Ti/TiO2 contains a significant amount of X-ray amorphous compounds on the surface, which are most likely hydrated titanium oxides. The main crystalline phase is titanium dioxide in the allotropic anatase form. Metallic titanium is present on the surface in trace amounts. Thermal treatment of this material at a temperature of 5000C for 3 hours in an air atmosphere leads to an increase in the proportion of the crystalline phase. The content of metallic titanium increases significantly, reaching about a third. A partial electrochemical reduction of nanotubes allows one to obtain more electrically conductive titanium suboxides. After cathodic reduction of nanotubes for one hour, a coating with metallic platinum is uniformly deposited on the surface of the material. Thermal treated Ti/TiO2 nanotubes are an n-type semiconductor with a flat-band potential equal to –0.589 V and a carrier concentration of 61020 cm–3. Such a high concentration of carriers is obviously due to the small thickness of the oxide film and its nonstoichiometry, as a result of which the surface is not very depleted in electrons, since titanium metal acts as their donor.