MONITORING OF HF AND F2 USING A FIELD-EFFECT SENSOR

A sensor for the determination of fluorine and hydrogen fluoride in ga ses has been developed. Lanthanum fluoride and platinum are used as th e gate materials in a field-effect device with silicon in direct conta ct with the ionic conductor. The determination of both gases is possib le at room temperature in the ppm concentration range. The response ti me of the sensor is of the order of some minutes. Oxygen, which can al so be determined with a similar sensor system, does not interfere. The influence of thermal activation is proved to be different for the two analytes. Selectivity for HF and F-2 can be achieved because of a ver y high difference in the gate voltage in both gases and the influence of the on-chip activation process.