Ultrafast-response H2S MEMS gas sensor based on double phase In2O3 monolayer particle film

The regulation of crystal structure plays a crucial role in gas sensing. In this work, by precisely controlling the annealing temperature, we first synthesized rhombohedral corundum-type In2O3 (h-In2O3), cubic bixbyite-type In2O3 (c-In2O3) and double phase In2O3 (c/h-In2O3). The c/h-In2O3 possesses the heterostructures of double phases, the abundant oxygen vacancies (61.1 %), and the more adsorbed oxygen (35.9 %). Subsequently, by self-assembly method, the sensors with one monolayer In2O3 particle film were successfully fabricated. The c/h-In2O3 sensor shows excellent H2S sensing performances with high response of 54.4 (50 ppm), extremely fast response time of 3.3 s and low limit of detection (LOD) of 20 ppb at 160 degrees C. The reasons for the ultrafast response of the sensor were unveiled through the comparison experiment of 4 layers particle film sensor and the theoretical analysis. Additionally, the outstanding sensing performance could be attributed to the abundant oxygen vacancies, the double phase heterojunction and the monolayer particle film. This work provides a new idea for designing micro-electro-mechanical system (MEMS) gas sensors with high sensitivity, extremely fast response, low power consumption and high level of integration.