Sulfureted Hydrogen Sensing Property Of Doped Tin Oxide Thin Films

The nano-crystalline tin oxide thin films doped with antimony and copper were prepared by the sol-gel dip-coating (SGDC) method, using cheap inorganic salts and absolute ethanol as the starting materials.The fabricating process of the thin films was studied, and some key parameters were defined by the XRD and TEM study and the resistance testing of the films. Stannous chloride, copper chloride, antimony trichloride were dissolved in absolute ethanol respectively, then the sols were mixed for a given doping level, heated and stirred for 5 hours. The concentration of Sn2+ in the sol was controlled as 0.57 mol/L by organic solvent evaporation. Then glycerol was mixed into the sol with the proper volume ratio. Cleaned substrates were dipped into the mixture, withdrawn slowly and dried in air at 120℃for 15 min. All layers were finally heated at 600℃for 120 min after the dip-coating and drying were repeated for 5 times.The proper doping of Sb and Cu in the films was studied. The 5 at% Sb-doped tin oxide films have the minimum resistance, which is about 70 k?. The 1 at% Cu-doped SnO2: Sb films exhibit the highest sensitivity, which is about 18.3 for 137 ppm H2S and about 2.7 for 13.7 ppm H2S at 250℃.The SnO2: Sb: Cu films were tested. The films exhibit the highest sensitivity at 140℃, which is 10 for 13.7 ppm H2S. Although the concentration of H2S is just 0.7 ppm, the films show an acceptable sensitivity which is about 3. The response time and recovery time are good. They are 8 s and 40 s respectively at 250℃, while at 140℃, they are 130 s and 530 s respectively.The XRD spectra and SEM micrographs show that films are composed of nanocrystalline grains, with an average size of about 30 nm.