Electrical and piezoresistive properties of titanium oxycarbide thin films for high-temperature pressure sensors

Abstract Numerous piezoresistive films have been investigated for high-temperature pressure sensors, yet there have been no reports of piezoresistive films that exhibit all of the desired characteristics. In this study, titanium oxycarbide thin films were deposited on quartz substrates via ion beam sputtering under various oxygen gas flow rates. The electrical and piezoresistive properties of the films were evaluated with the goal of applying this material as a piezoresistive film for high-temperature pressure sensors. By adjusting the oxygen gas flow rate during deposition, films with a gauge factor of approximately 4 and a temperature coefficient of resistance of approximately zero can be obtained. Hall-effect measurements revealed that the film exhibits degenerate electrical conduction within temperatures ranging from 298 K to 673 K in vacuum, suggesting that the film has a gauge factor with a low temperature dependence. A pressure sensor based on a three-layer film, in which a piezoresistive film is sandwiched between silicon carbide protective films, showed no decrease in the output voltage at temperatures ranging from 298 K to 673 K under air atmosphere.