Thin solid films semiconducting metal oxide gas sensors: A brief review

Gas sensors have been extensively used to detect, and monitor a wide variety of volatile and other radical gases. In particular, gas sensors have a enormous variety of applications such as in environmental quality control, public safety, medical applications, and automotive applications, and for air conditioning systems in aircrafts, spacecrafts, vehicles, and houses. Semiconducting metal oxides (MOs) such as indium oxide (In₂O₃), nickel oxide (Ni₂O₃), tin dioxide (SnO₂), titanium dioxide (TiO₂), and zinc oxide (ZnO) are used for gas sensing applications due to the sensitivity of their electrical conductivity to the ambient gas composition, which arises from charge transfer interactions with reactive gases such as oxygen (O₂), mono-nitrogen oxides (NO_x), carbon monoxide (CO), hydrocarbons (HC), volatile organic compounds (VOC), and ozone (O₃). In the present review, the emphasis is on the recent trends to develop sensors mainly fabricated considering thin solid films semiconducting metal oxide.