Sensing of CO2 at room temperature using work function readout of (hetero-)polysiloxanes sensing layers

Organically modified silicates based on primary amino groups are known to be CO2 sensitive, as they can undergo a reversible acid base reaction. In order to generate detectable CO2 signals and to limit the cross-sensitivity to humidity, some sources suggest that these materials should be operated at higher temperatures (50–70 °C). In this paper, a new variant of CO2 sensing is to be presented, namely a combination of work function readout and organically modified silicates, which yields CO2 detection even at room temperature. Kelvin probe measurements are used for work function readout. The layers are intended to be used in a “Floating Gate Field Effect Transistors” (FGFETs) sensing platform (mySens) by Micronas. The reversible interaction of CO2 with spin-coated heteropolysiloxane sensitive layers results in changes of the work function with typical signal heights of 15–20 mV (change from 400 to 4000 ppm CO2) and response times of only a few minutes. Also, results will be presented regarding variations in the chemical nature of the films. The findings summarized in this paper point towards the possibility of a new room temperature CO2 sensor, which comprises fast response times and sufficient sensitivity for ambient CO2 variations.