Silicon-based micro-gas sensors for detecting formaldehyde

Micro-formaldehyde gas sensor of palladium doped tin dioxide was fabricated on silicon 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 μm and the width of the central seven strips 25 μm. 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 Oa/Ol, i.e., the ratio of adsorption and lattice oxygens. Formaldehyde of 0.03 ppm concentration was detected by the 1 mol% Pd-doped SnO2 micro-gas sensor.