Gas-sensing properties of semiconductor heterolayers fabricated by a slide-off transfer printing method

Single layers, multilayers and heterolayers of SnO2-based materials were fabricated by a slide-off printing method and their sensing properties to 1% H-2 in air were investigated. By selecting an appropriate combination of materials for the lower and upper layers of a heterolayer sensor, the sensitivity or the resistance decrease upon exposure to H-2 could be enhanced at temperatures above 300 degrees C, compared with those of the constituent single layers. In a heterolayer sensor of SnO2/Pt-SnO2, the upper SnO2 layer was suggested to enhance the sensitivity of the Pt-SnO2 underlayer by functioning as a filter for O-2 permeation. At 200 degrees C, on the other hand, most of the sensors fabricated exhibited a tendency for the resistance to increase upon exposure to H-2, probably due to negatively charged chemisorption of H-2. (C) 2000 Elsevier Science S.A. All rights reserved.