Semiconductor sensors for fluorine detection — optimization for low and high concentrations

For the detection of fluorine, two different preparation methods for semiconductor gas sensors were developed, the first for concentrations between 10 and 1000 ppm (type I) and another for concentrations between 0.01 and 10 ppm (type II). The sensitivity of type I sensors is about 116 mV/lg(p(F2)). It is possible to detect gas concentrations down to 0.1 ppm using this sensor. The main disadvantage is that the sensor response kinetics depends strongly on concentration. The sensors response is fast for measurement of high concentrations (between 10 and 1000 ppm) but the response time is not acceptable for the detection of small concentrations. Type II sensors show a sensitivity of 28 mV/lg(p(F2)) for gas concentrations between 0.006 and 10 ppm. This sensor is very fast in the detection of small concentrations of gas.