Gas Sensing Properties of Al2O3/SnO2/SnO2 Multilayered Films Modified with Pt.

Abstract

Al2O3/SnO2 multilayered films were fabricated via the sol-gel method using iPrOH solutions of Sn(iOPr)4 and Al(iOPr)3, which were prepared by adding triethanolamine. Coating was accomplished by a dip-coating procedure. Doping with Pt and surface modification of SnO2 films by Pt were also performed. The Al2O3 layer was coated on the SnO2 film to fabricate Al2O3/SnO2 multilayered films. The SnO2 film, after five depositions and firing at 600°C, was about 400nm in thickness and 20-30nm in grain size. The Al2O3/SnO2 multilayered gas sensor exhibited higher gas sensitivity than the monolithic SnO2 film, particularly to CH4. The increase in the sensitivity was due to the high resistivity in air atmosphere when the Al2O3 layer was overcoated. The doping of Pt into the SnO2 film negligibly affected the sensitivity, except that to CH4, though SnO2 film surface-modified with Pt film exhibited high gas sensitivity even at low temperature. The multilayered film of Al2O3/Pt/SnO2 exhibited high sensitivity to CH4 and fast changing speed.