Enhancements of Humidity and Gap-Sensing Properties of Coil-Shaped SnO2 Based on Layered Sputtering Method

To promote the application of simultaneous measurement of humidity and gap, by a single coil-shaped SnO2, it makes efforts to improve the sensing performance of coil-shaped SnO2 by studying the sputtering duration and layered structure. First, the dependence of sputtering duration on the sensing performance of coil-shaped SnO2 is obtained through experimental analysis. Second, a layered sputtering process (30 min of Sn sputtering on the bottom layer and 60 min of SnO2 sputtering on the surface layer) is designed and experimentally verified according to the sputtering duration rule. The results show that: 1) an optimal sputtering duration of 60 min for humidity and 120 min for gap-sensing results in peak sensitivities; 2) compared to single-layer sputtering, the layered sputtering approach enhances the humidity-impedance response sensitivity by 1.68 times, achieving 0.146/%RH, diminishes hysteresis to 28.73%, and reduces the response time to 4 s; and 3) the gap-impedance response sensitivity is amplified by a factor of 10.09, reaching 36.01%/mm. This study introduces a cost-effective advancement in the fabrication process, significantly boosting the sensing performance of coil-shaped SnO2.