Study On Fabrication Technology And Properties Of Nanocrystalline SnO₂ Gas-sensing Films

In this paper, screen-printing technology and Aerosol-Assisted Chemical vapor deposition were used to fabricate gas sensor, the properties of the sensors were deeply researched.Nanometer SnO2 and In2O3 powder were prepared through hydrothermal method. SnO2 powder doped with microdosage nanometer In2O3 and Sb2O3 was prepared into paste, then, was fabfricated into thick film and annealed at 700℃。XRD,SEM were used to analyse the microstructure of the films, the result showed that the particle size of the SnO2 nanoparticles on the film was 10 nm, the surface of film was porous. Gas-sensing testing of the film indicated that sensors which doped with 7 wt% In2O3 obtained the best gas-sensing properties: the film could identify 2 ppm H2S at 40℃and the sensitivity was 2.66; To 30 ppm H2S, the sensitivity reached 621, the sensor responsed quickly and could recover well after thermal cleaning. In2O3 and TiO2, Al2O3 doped thick films also were fabricated through hydrothermal, the sensors could detect 300 ppm and 500 ppm CH4 gas.Alcohol solution of SnCl2 was used as precursor, thin films were prepared by AACVD. The effect of depositing time, depositing temperature, concentration of solution on the conductivity and gas-sensing properties of the film were studied. The optimizing preparation method was generalized. The thin films also obtained excellent gas-sensing properties: the sensitivity to 50 ppm H2S at 25℃reached 97, the voltage change could response 90% without thermal cleaning.Alcohol solution of Cu(CH3COO)2 was used as precursor, CuO doped thin films were fabricated through AACVD. The effect of doping mode, depositing time, annealing temperature on gas-sensing properties of the film were studied. The optimizing doping process was concluded. SEM analysis indicated that the thin films were multihole, the average grain size was about 40 nm. The recovering/response properties to H2S at room temperature of the CuO doped thin films showed great improvement. At 25℃,the sensitivity to 5 ppm and 100 ppm H2S were 3.7 and 928 individually. Without thermal cleaning, the response time and the recovery time to 100 ppm H2S gas were100 s and 130 s individually. At last, the gas-sensing mechanism to H2S gas of thin film prepared by AACVD was analyzed by non-stoichiometric chemistry.