Highly sensitive MISFET sensors with porous Pt–SnO2 gate electrode for CO gas sensing applications

Novel devices based on a porous Pt–SnO2 metal–insulator–semiconductor field-effect transistor (MISFET) for carbon monoxide (CO) gas sensing have been proposed. The structure integrates the catalytic properties of porous Pt, a thin catalytic layer, and the spillover effect onto SnO2, a gas adsorptive oxide, with surface-sensitive MISFETs. The operation characteristics of the device for the detection of CO gas are presented as a function of CO gas concentration and operating temperature. The threshold voltage decreased rapidly with time when the device was exposed to CO gas depending on the operating temperature. It was possible to detect 54 ppm of CO gas with a response time of less than 1 min at 27°C. A model was proposed to explain the operation. The proposed sensing mechanism of the device is supported well by experimental data.