Effect of pre-heating conditions on MOS gas sensors towards acetone vapor

Oftentimes, gas sensors based on semiconductor metal oxide (MOS) materials are essentially pre-heated at elevated temperatures and the total heating power, pre-heating conditions, and response time and/or reversibility are crucial parameters of a given MOS gas sensor. In this study, we examine the impact of pre-heating conditions on the overall sensing performance of gas sensors based on SnO
2
thin films. The sensors were initially pre-heated to 1, 2, and 3 hours and the corresponding gas sensing properties towards acetone vapor were investigated. The results show that MQ2 sensors exposed to acetone vapor recover faster (T
rec
) for a 1-hour pre-heating than for a 2-hour pre-heating condition. In contrast, the sensor shows faster response time (T
res
) for longer pre-heating conditions. This is mainly attributed to the increase of surface-active sites by lowering the activation energy over longer preheating conditions. In contrast, a 1-hour preheating of the MQ7 sensor depicted faster response T
res
acetone gas exposures while MQ135 recorded a T
res
of 172 sec after a 2-hour preheating. Notably, each sensor provides characteristic response and recovery times over different preheating conditions. Thus, our results revealed that the performance of MOS sensors are greatly affected by the pre-heating conditions during gas-sensing measurement.