Investigation of low-temperature deposition of SnO₂ thin film for improving sensitivity of LaOCl/SnO₂ heterojunction CO₂ sensor using electrochemical impedance spectroscopy

In this study, LaOCl/SnO₂ heterojunction CO₂ sensors were fabricated by spin-coating LaOCl onto a SnO₂ thin film fabricated via RF magnetron sputtering. The sensitivity of LaOCl/SnO₂ heterojunction CO₂ sensors tended to improve with the deposition of SnO₂ thin films without intentional heating (at approximately 35 °C). Electrochemical impedance spectroscopy measurements revealed that the formation of a LaOCl/SnO₂ heterojunction interface is indispensable for high-sensitivity sensors, and LaOCl acted not only as a catalyst but also as a capacitive layer in the sensors. The capacitive element of the LaOCl/SnO₂ heterojunction changed under a CO₂ gas atmosphere. It is confirmed that the formation of heterojunction interfaces contributes to the improvement of sensitivity. The results of this study indicate the potential applications of heterojunction gas sensors.