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

Abstract

Al 2 O 3 /SnO 2 multilayered films were fabricated via the sol-gel method using i PrOH solutions of Sn( i OPr) 4 and Al( i OPr) 3 , which were prepared by adding triethanolamine. Coating was accomplished by a dip-coating procedure. Doping with Pt and surface modification of SnO 2 films by Pt were also performed. The Al 2 O 3 layer was coated on the SnO 2 film to fabricate Al 2 O 3 /SnO 2 multilayered films. The SnO 2 film, after five depositions and firing at 600°C, was about 400 nm in thickness and 20-30 nm in grain size. The Al 2 O 3 /SnO 2 multilayered gas sensor exhibited higher gas sensitivity than the monolithic SnO 2 film, particularly to CH 4 . The increase in the sensitivity was due to the high resistivity in air atmosphere when the Al 2 O 3 layer was overcoated. The doping of Pt into the SnO 2 film negligibly affected the sensitivity, except that to CH 4 , though SnO 2 film surface-modified with Pt film exhibited high gas sensitivity even at low temperature. The multilayered film of Al 2 O 3 /Pt/SnO 2 exhibited high sensitivity to CH 4 and fast changing speed.