Structural and Electrical Properties of Flexible ITO/In₂O₃Thermocouples on PI Substrates under Tensile Stretching

The development of modern science and technology poses a challenge to temperature sensors for more convenient and accurate temperature measuring, especially for flexible devices. The in-situ temperature measurement technique has been extensively studied to solve this problem. In this work, In2O3 and ITO thin films were deposited on polyimide substrates to form transparent flexible thin film thermocouples by radio-frequency magnetron sputtering. A variety of transmissions, surface morphologies, and resistances of In2O3 and ITO films were investigated during tensile experiments. The increasing tensile strain leads to an increase in the resistance of the two kinds of electrode films in different ways. The In2O3/ITO flexible thin film thermocouples still keep good thermoelectric response and high Seebeck coefficient after the tensile test with an applied strain up to 0.7968%. Whereafter, the finite element simulation method was employed to calculate the cohesive toughness of In2O3 and ITO films to investigate the mechanism of crack initiation and propagation. The facile preparation processing and good thermoelectric response of the In2O3/ITO flexible thin film thermocouples made them a promising candidate in the application of in-situ temperature sensing in electronic components and wearable devices.