Ozone sensing properties of thermally evaporated In₂O₃-based thin films

Ozone sensing properties of mixed oxides of In₂O₃, ZnO, and SnO₂ in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization (WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In₂O₃, ZnO, and snO₂ were deposited in a rectangular pattern on top of copper interdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.