Microstructured Carbon/SiCX (X=O, N)-Based High Temperature Strain Gauge

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The project aims to develop micro-sized strain gauges applicable at elevated temperatures (T > 400 °C) addressing both basic and application-related research. The project is mainly focused on the investigation of the piezoresistive effect of C/SiCX (X = O, N) nanocomposite thin layers with 13 to 20 vol% carbon as well as enabling the realization of high-temperature stable sensor structures superior to the state-of-the-art piezoresistive sensors based on silicon. The synthesis and characterization of C/SiCX thin films with a thickness of ~1 µm and their integration in a laboratory sensor test structure will be realized. Silicon cantilevers, spin-coated with C/SiCX thin films, will be used as piezoresistive sensor elements. Their performance will be assessed using a 3-point bending test setup, which will be designed and built for this specific purpose. To enable 4-point measurements of the resistance of the C/SiCX-based ceramic film, high temperature stable connections will be developed and characterized. Furthermore, the crosstalk between the single measurement elements will be investigated, as they are placed on top of an unstructured high impedance piezoresistive C/SiCX layer. The bending tests, including measurements of the gauge factor for both tensile as well as compressive stress, will be performed in a temperature range spanning from room temperature up to 800°C. The tests of the sensor elements will be combined with structural characterization e.g. crack formation under mechanical stress and its evolution concerning composition and thickness in corrosive atmospheres. In a subsequent project, the results from the silicon cantilever experiments can be transferred to the actual application of a backside etched silicon membrane sensor with the piezoresistive C/SiCX layer.