Thin Film Strain Sensors with Significantly Improved Piezoresistive Stability at High Temperatures by Introducing Insulating Phase

In this work, we propose a strategy to significantly enhance the piezoresistive stability of indium tin oxide (ITO) thin film strain sensors (TFSSs) at high temperatures. Al₂O₃, known for its excellent thermal stability in harsh environments, was introduced into ITO matrices to form composite films. The effect of doping concentration on the crystal structure, surface morphology, electrical stability, and piezoresistive stability of ITO TFSSs were systematically investigated. Results reveal that the addition of Al₂O₃plays an important role in restraining recrystallization and reducing growth defects in ITO films at high temperatures, which leads to a remarkable improvement in piezoresistive stability by one order of magnitude. The idea disclosed in this work is of great significance for the design, fabrication, and enhancement of micro/nano piezoresistive sensors that operate in harsh environments.