Photoconducting properties of individual single crystalline Sn3O4 nanobelts were investigated by performing transport measurements. The nanobelts were found to exhibit large responsivity under ultraviolet (UV) illumination: the electric current in one single nanobelt greatly increases by about three orders of magnitude. Such photoconductive behaviour was ascribed to the photogeneration of electron-hole pairs and to surface effects such as the oxidation and photoreduction of oxygen molecules (trapping). These mechanisms were found to be drastically modulated by the presence of oxygen vacancies which generates additional energy states that provide free electrons for conduction in these samples. In fact, the use thermally stimulated current spectroscopy was found to be a powerful tool for the study of additional energy levels on Sn3O4 nanobelts as a guide to applying this technique to any high-resistivity nanomaterial. The experimental data provided two vacancy-related levels in 0.01 and 0.2eV. On the basis of the transport measurements, a qualitative model was proposed in order to explain the response of these samples to UV light.

Detection of Oxygen Vacancy Defect States in Oxide Nanobelts by using Thermally Stimulated Current Spectroscopy. O.M.Berengue, M.K.Kanashiro, A.J.Chiquito, C.J.Dalmaschio, E.R.Leite: Semiconductor Science and Technology, 2012, 27[6], 065021