Oxygen related defects excitation and photoconductivity dependence of SnO2 Sol-Gel films with several light sources

Since oxygen vacancies act as donors in SnO 2 , the electrical properties are related to deviation from stoichiometric composition. Depending on stoichiometry SnO 2 can be highly insulating or may exhibit fairly high n-type conductivity. Since bandgap transitions are in the ultraviolet range, its photoconductivity is strongly dependent on the excitation source. We have measured variation of photoconductivity excitation with wavelength for tin dioxide grown by dip-coating sol-gel technique using several light sources: tungsten lamp, xenon, mercury and deuterium, and present selected results. The main band is obtained in the range 3-4 eV according to light source spectrum in the ultraviolet range. The presence of oxygen in the cryostat also affects the spectrum since electron-hole pairs react with adsorbed oxygen specimens.