Semiconducting gas sensor incorporating a sparking decomposer

Abstract

In this article a new method is demonstrated for improving gas sensor characteristics. An electronic sparker is included in a semiconducting SnO 2 thin-film sensor system for cracking the gas molecules to be detected. The distance between the electrodes is 0.2 mm, which conforms to a 1–1.8 kV breakdown voltage at 0.1–0.5 mA coming from a current-limited power supply. A good correlation exists between the characteristics of this composite sensor system and the structure of detectable gas molecules. For small gas concentrations (below 1% for CH 4, 0.01% for normal C 6H 14 and C 4H 10) the sensor resistivity increases due to the spark discharge, as well as in clean air. At moderate and high concentrations of hydrocarbons, the spark discharge improves the sensitivity, depending on the structure and the hydrogen content of the molecule. Chlorine and other halogen-containing gases and solvent vapours, such as CCl 4, CHCl 3, CH 2Cl 2 and CF 2Cl 2, also yield a higher resistivity after sparking, even at high concentrations (5% or more).