The influence of gate bias and structure on the CO sensing performance of SiC based field effect sensors

SiC based Field Effect Transistor gas sensors with Pt as gate material have previously been shown to exhibit a binary CO response, sharply switching between a small and a large value with increasing CO or decreasing O₂ concentration or temperature. In this study Pt gates with different structures have been fabricated by dc magnetron sputtering at different argon pressures and subjected to various CO/O₂ mixtures under various temperatures and gate bias conditions. The influence of gate bias and gate structure on the CO response switch point has been investigated. The results suggest that the more porous the gate material or smaller the bias, the lower the temperature or higher the CO concentration required in order to induce the transition between a small and a large response towards CO. These trends are suggested to reflect the adsorption, spill-over, and reaction characteristics of oxygen chemisorbed to the Pt and insulator surfaces.