Abstract
We have demonstrated the ability of thin nanocrystalline SiC films with various types of conductivity to detect oxidative (O2), reducing gases (CO, CH4) with the maximum allowable concentrations for human safety. It was shown that n-nc-SiC films with electronic conductivity had a higher gas sensitivity Sn than p-nc-SiC films with hole conductivity sensivity Sp to the action of gases in a wide concentration range. So, for the maximum permissible concentrations of O2 (3%), CO (0.1%), CH4 (10%) the sensitivity ratio of the films Sn/Sp was 2.9; 4.8 and 10, respectively. For research, we used a simple resistor geometry optimizing which it is possible to significantly increase the sensitivity of films to gases in order to detect extremely low gas concentrations. Thus, based on nc-SiC films, it is possible to develop high-temperature gas sensors to detect reactive gases in a wide range of concentrations, including threshold allowable values.
Highlights
Silicon carbide (SiC) has high potential as an electronic semiconductor material for a new generation of high-temperature sensors and power electronics devices
Earlier we presented the first results of the study of chemical resistance sensitivity of thin nanocrystalline SiC (nc-SiC) films to air atmosphere gases [11]
On p-nc-SiC films with hole conductivity a lower sensitivity of the resistance to the action of gases was observed
Summary
Silicon carbide (SiC) has high potential as an electronic semiconductor material for a new generation of high-temperature sensors and power electronics devices. The high sensitivity of SiC sensors to many toxic and dangerous gases makes them indispensable for monitoring the gas atmosphere in high temperature (> 800°C) processes in space, aviation, automotive, chemical and physical reactors [7]. These applications require sensor’s reliable operation in various difficult conditions: from cryogenic temperatures to more than 800°C, from chemically inert media to highly aggressive engine emissions and from the detection of one gas in a wide range of concentrations in inert media to the detection of several gases in narrower ranges of concentration in the presence of interfering gases. At the same time high sensitivity, long-term stability, good reproducibility are necessary The combination of these requirements was achieved on the sensors developed on monocrystalline SiC [1, 7]. The high cost of technology for SiC monocrystalline sensors limits their wide application
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