Silicon-based micro-gas sensors for detecting formaldehyde

Micro-formaldehyde gas sensor of palladium doped tin dioxide was fabricated oil si I icon Substrate. Finite element software ANSYS was used to analyze the thermal field distribution. In order to obtain a uniform thermal field distribution in the micro-gas sensor, the width of the marginal four strips of the heating electrode was designed to be 50 mu m and the width of the central seven strips 25 mu m. Undoped and 1 mol% Pd-doped SnO2 thin films were synthesized by sol-gel method on silicon Substrates. XRD and XPS spectra of the films were analyzed. The response of the 1 mol% Pd-doped SnO2 micro-gas sensor to formaldehyde was much higher than that of the undoped SnO2 micro-gas sensor. This experimental observation was also supported by the XPS O (1s) patterns of the films which showed that doping 1 mol% Pd into SnO2 increased the value of O-lambda./O-l, i.e., the ratio or adsorption and lattice oxygens. Formaldehyde of 0.03 ppm concentration was detected by the 1 mol% Pd-doped SnO2 micro-gas sensor. (c) 2008 Elsevier B.V. All rights reserved.