Microstructural Engineering Enables Record Thermal Endurance of Metal Oxide Thin Films in Extreme Environments

High-temperature thin-film sensors (HTTSs) offer promising solutions for in situ monitoring of various thermal and mechanical parameters in extreme environments. However, maintaining their stable operation at high temperatures exceeding 1000 °C for extended durations remains challenging due to severe material degradation. This study first demonstrates a microstructural engineering strategy to enhance the thermal endurance of metal oxide thin films through integrating high-melting-point metal oxide nanophases. Using standard Micro-Electro-Mechanical System (MEMS) technologies, alumina (Al₂O₃) is atomically integrated into indium tin oxide (ITO) thin films. The influence of Al₂O₃ doping on the ITO matrix under various high-temperature conditions, with emphasis on the variations of chemical composition, crystal structure, morphology, recrystallization, and sensing behavior, is systematically investigated. An optimized film, characterized by an Al/In ratio of 1.57 wt.%, exhibits a record-low resistance drift of 0.002% h⁻¹ during a 10 h exposure at 1200 °C.