Electronic structure of titanium oxide nanotubules

We investigated the electronic states of titanium oxide nanotubules (TiOx-NTs) by using field induced surface photovoltage spectroscopy (FISPS). Compared with common TiO2 P25 nanocrystals, new surface photovoltage response bands extending to 550 nm were found under the effect of external electric field. Based on the principle of FISPS, these responses were ascribed to the surface state transitions. X-ray diffraction (XRD) indicated that the crystalline structure changed remarkable during the hydrothermal synthesis process. The existence of oxygen vacancies contributing to the surface states was further confirmed by the sub-band gap photoluminescence.