from 300 ppm to 1000 ppm it assumes a value of 260 Hz/ppm. The range from
1000 ppm to 5000 ppm is 115 Hz/ppm.
CONCLUSION
The analysis of physical processes on the surface of semiconductor gas sensors
has shown that in the formation of the subsurface layer of spatial charge there are
excessive mobile charge carriers - electrons and holes, so the specific surface resistance
is determined by their concentration, multiplied by the corresponding motility and
elementary charge. On the other hand, the change of the charge in the layer of spatial
charge at the change of the surface electrostatic potential is characterized by the
introduction of the concept of differential capacity of the layer of spatial charge. Thus,
the total resistance of semiconductor gas sensors consists of a parallel connection of
the capacity of the surface layer of the spatial charge and near-surface resistance.
Change of total resistance of semiconductor gas transducers with frequency
output signal from change of concentration of measured gases characterizes gas
reactive effect of transducers, unequivocally changes output frequency of
autogenerator gas transducers. The transformation functions and the sensitivity
equation of the device were determined, with a sensitivity of 260 Hz/ppm in the range
of 300 ppm to 1000 ppm, and in the range of 1000 ppm to 5000 ppm – 115 Hz/ppm.
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