Stone-Based Substrates for Thin-Film Thermistor Temperature Sensors

This work reports on the potential of using stone-based substrates including marble, brick, stone paper, and Limex paper for the fabrication of thin-film sensors, in particular thermistors. The thermistors were fabricated by 100 nm Cu and 30 nm InGaZnO sputtered thin-films with the exception of the Limex substrate where the optimized InGaZnO layer turned out to be 50 nm. The resistance of these thermistors at room temperature varied significantly, with values of 65 kΩ, 125 kΩ, 400 kΩ, and 1 kΩ observed for marble, brick, and the two stone papers, respectively. The characterization of the thermistors' performance was carried out within a temperature range of 25 °C to 80 °C. The two flexible thermistors, stone paper, and Limex, showed larger hysteresis. The brick thermistor showed the largest sensitivity. Moreover, the marble and stone paper demonstrated stable behavior in the cycling test. Additionally, the flexible stone paper thermistor showed an increase in resistance as the bending radius decreased up to 25 mm. As a result of the findings, stone-based materials have the potential to be used as natural substrates for temperature sensors.