Influence of multi-layer TiO2/SnO2 heterojunctions on fast and sensitive ethanol detection

The fabrication of MEMS gas sensors based on SMO sensing materials has become popular in commercials. However, due to the dense surface, the MEMS gas sensor based on sputtered sensing film always shows low sensitivity and slow response. Herein, we report multi-layer TiO2/SnO2 heterojunctions sensing film deposited by sputtering techniques. SnO2 and TiO2 thin film have an approximate thickness of 265.34 nm and 66.28 nm, respectively. The effects of different-layer TiO2/SnO2 heterojunctions and annealing temperatures to sensing film on gas sensing properties were investigated. The different samples with the same surface and annealed tem-perature exhibit different gas sensing properties, which indicates that more layer heterojunctions may decrease the positive effects of heterojunctions and oxygen adsorptions on the gas sensing properties. The two-layer TiO2/ SnO2 heterojunctions sensing film with an annealed temperature of 400 degrees C in air obtain the best gas sensing properties, which has a response value of 7.54 and response/recovery time of 33/298 s to 50 ppm ethanol at 260 degrees C. Furthermore, the MEMS gas sensor based on two-layer TiO2/SnO2 heterojunctions sensing film can detect ethanol ranging from 1 ppm to 1000 ppm with excellent linearity.

Automated summary

The fabrication of multi-layer TiO2/SnO2 heterojunctions sensing film using sputtering techniques and its gas sensing properties were investigated. The two-layer TiO2/SnO2 heterojunctions sensing film annealed at 400 degrees C exhibited the best gas sensing performances, with a response value of 7.54 and response/recovery time of 33/298 s to 50 ppm ethanol at 260 degrees C. The MEMS gas sensor based on this sensing film showed excellent linearity in detecting ethanol ranging from 1 ppm to 1000 ppm.