Reactively sputtered InxVyOz films for detection of NOx, D2, and O2

Depletion-mode 4H-SiC field effect transistors (FETs) responding down to 0.002 mbar of NOx gas at a temperature of 300 °C were realized. A mixture of indium oxide (InOx) and vanadium oxide (VOx) was deposited by RF magnetron reactive sputtering as a gate material. The responses to NOx, D2, and O2 gases were investigated as a function of the operating temperature for different partial pressures of the test gases. The sensor is very sensitive to NOx and its performance is strongly dependent on the gas concentrations and operating temperature. The response to D2 has been found to be maximal at room temperature. The optimum detection temperatures occur in the range 275–325 °C for NOx with these catalysts. The response to both O2 and D2 is very low in this temperature range, suggesting that the sensor is very suitable for selective detection of NOx. The optimum temperature of operation for detection of D2 is determined to be between 25 and 100 °C. In this range no significant responses to O2 and NOx are observed, indicating that the sensor is very suitable for D2 detection at very low temperatures.