Response of a thermocatalytic sensor with a single-crystal silicon heater

The sensor response of a thermocatalytic gas sensor with a heater made of single-crystal p-type silicon to gases H₂, CO, CH₄, and C₃H₈ is studied. The sensor response to propane, carbon monoxide, and hydrogen has positive and negative components. The positive sensor responses to carbon monoxide and propane exhibit well pronounced maxima at silicon heater currents of 21 and 23 mA, respectively. For hydrogen, the maximum sensor response depends on the gas concentration. This specific feature of the sensor response to hydrogen is explained by the sequential action of the following two processes: absorption of H₂ molecules on the silicon heater surface and the catalytic oxidation of hydrogen on a Pt-Pd catalyst. The sensor response to methane only has a negative component.