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

Abstract

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.