Binary and ternary metal oxide semiconductor thin films for effective gas sensing applications: A comprehensive review and future prospects

For a couple of decades, there is a tremendous growth in industries and technology in the global level. Unfortunately, emerging new industries became a main reason for rising air pollution in the earth's environment. Hence, the health issues associated with air pollution are on a high scale that alarm us to monitor the quality of the air that we breathe, and demand development of efficient gas sensor devices. Recently, the groups of binary and ternary metal oxide semiconductors are regarded as reliable materials for gas sensing applications. Chemical spray pyrolysis, one of the efficient techniques to fabricate thin films with high reproducibility is triggering recent research on fabricating films for gas sensor applications. Here, the focus is on spray-deposited binary and ternary metal oxide thin films for gas sensing applications. The working mechanism of metal oxide sensors have been discussed comprehensively on the basis of redox reaction processes that caused band bending and variation of electrical conductivity of devices in the presence of target gases. This review also points out the shortcomings of existing technology and the possible ways to overcome them, and eventually future evolution in the field of gas sensor are also hypothesized.