Functional Oxide Pressure Sensor

Manganites are well known in the oxide community, especially La2/3Sr1/3MnO3 (LSMO) for its magnetic behavior above room temperature. In these materials, electrical conduction is due to several phenomena such as double exchange or polaronic conduction that give rise to a modulation of the material’s resistivity with the temperature. Measuring the resistance of a device can thus be a way to measure its temperature and was notably used to design bolometers working at room temperature, thanks to its high Temperature Coefficient of Resistance (TCR) close to the ferromagnetic transition. For suspended microdevices, dependence on the background gaz pressure is also observed. This phenomenon relates to the Pirani effect where the surrounding gas cools down the heated device because the local thermal conductivity depends on ambient gas pressure. Close to the ferromagnetic transition, the TCR of LSMO is almost a decade higher than Platinum making this material a good candidate for sensor application at room temperature. Additionally, the high chemical stability of manganites and their very low intrinsic electrical noise level are other arguments to use them in this field. Micro-pirani sensors were fabricated thanks to the integration of LSMO on Si with STO and YSZ buffer following by MEMS technology processes. Such oxide-based sensors exhibit sensitivity 10 times better and power consumption reduced by a factor of 100 with respect to a metallic sensor with the same geometry.