H 2S sensing property of porous SnO 2 sputtered films coated with various doping films

Abstract

Pure SnO 2 films and Ag-, Cu-, Pt-, and Pd-doped SnO 2 films were investigated for H 2S sensing properties. SnO 2 films were deposited by DC magnetron sputtering at various substrate temperatures and discharge gas pressures. As the discharge gas pressure increased and the substrate temperature decreased, the film became porous. Doping with Cu or Ag film improved the sensitivity, and the highest sensitivity was obtained in the porous SnO 2 film coated with an Ag film 16 nm thick. According to the X-ray diffraction (XRD) pattern, Ag deposited on SnO 2 film transformed to Ag 2S upon exposure to H 2S. When the Ag-doped film sensor was operated at a low temperature, the sensitivity was extremely high, but the recovery was insufficient. By increasing the operation temperature, the recovery was improved but the sensitivity decreased.