A Hybrid In 2 O 3 /Cu-Based Thin-Film Thermocouple for Real-Time Sensing Applications

This work presents a hybrid thin-film thermocouple designed on a glass substrate employing a metal (Cu) and metal-oxide material (n-type In₂O₃) combination. The structural properties indicate that making a BCC (In₂O₃)-FCC (Cu) junction with different crystallite sizes is a suitable alternative to achieve high thermoelectric performance. The electric and thermoelectric properties revealed a power factor of 100.91 μW/mK² for In₂O₃ and 2.08 μW/mK² for Cu. Here, In₂O₃ benefits from its high Seebeck coefficient, while Cu contributes to superior electrical conductivity, making their combination promising for thermoelectric sensor applications. In addition, a two-leg thin-film thermocouple was developed, and its performance was explored. Also, the origin of the highest sensitivity (~115 μV/K) in this kind of hybrid thermocouple using band-theory diagrams was discussed. Further, we obtained an output power of 0.38 nW with an optimal current of 0.23 μA at ΔT of 35 K, making it suitable for low-power electronic IoT applications, such as self-powered sensors and energy-harvesting devices. The temperature measurements of ice-filled beaker and human body temperature show high sensitivity, excellent stability, long-term reliability, and superior performance of the thermocouple and make it a promising candidate for real-time and fast temperature-sensing applications.