Development of a Method of Increasing the Sensitivity of Gas Sensors

In this paper, the frequency dependences of the capacitance of the multilayer structure of matrix sensors with thick layers of porous semiconductor in vacuum and gas medium (hydrogen, carbon dioxide) are studied, it is determined that in vacuum the capacitance changes little with frequency variation. When the sensor is moved to the environment of H2 or CO2 with a concentration of 100 to 10000ppm C(f), the characteristics of the matrix sensor shift towards high capacitance values, and with increasing concentration, the capacitance is weakly dependent on frequency in the low frequency region and changes significantly at 103 Hz. The higher the concentration, the more high-frequency region shifts the area of sharp increase in capacitance. A method of processing signals from porous matrix sensors is also proposed, which is characterized by the use of polyharmonic power supply with a tuned set of frequencies, which allows to reduce the capacitance of the measured structure to the capacitance of the porous semiconductor layer and directly measure the dielectric constant of the porous layer. An important feature of the method is the use of a wide range of frequencies (102–106 Hz), at which the change in C(w), due to adsorption of gases, and takes into account only slow processes of current transfer in the gas-sensitive semiconductor material, which determines the corresponding change in the elements of the equivalent electrical circuit, including CPE.