Performance-oriented thickness engineering in ITO/In₂O₃ thin-film thermocouples: From thermoelectric enhancement to practical application

Optimizing the temperature sensing performance of thin-film thermocouples (TFTCs) is essential for stable output and high-resolution sensing under harsh thermal conditions. Conventionally, the performance of ITO and In₂O₃ films has been tuned via compositional doping and interface engineering, which often involve complex fabrication and limited controllability. Here, we propose a thickness-engineering strategy for performance enhancement. A literature survey reveals a scale-dependent correlation between film thickness and the Seebeck coefficient, with a theoretical explanation proposed to account for this phenomenon, corroborated by characterizations. We then fabricated ITO/In₂O₃ TFTCs with varying thicknesses and tested them at 1100 ℃, confirming that increased thickness enhances the Seebeck coefficient, reaching a maximum of 66.79 μV/℃. By optimizing film thickness, a maximum temperature measurement repeatability of 99.86 % and a minimum drift rate of 0.98 ℃/h were achieved. Finally, we demonstrate the feasibility of constructing a TFTC using a single material with varying thicknesses.