Tin dioxide thin film gas sensor

Abstract

Tin dioxide (SnO2) is the singular, most important material utilised in commercially manufactured sensors for toxic and combustible gases. In the present work, tin dioxide thin film sensors with porous microstructure and thickness of 0.22 μm have been fabricated on commercially available glass slides by a novel, low-cost, modified chemical deposition technique. Here we report, for the first time, the details of structural and deposition characteristics of the same films as a function of experimental parameters such as the number of dippings, bath temperature and bath concentration. In addition, the electrical properties were studied for both as deposited and palladium sensitised films as a function of temperature (300–500 K) in a closed quartz tube furnace. Further, the gas sensitivity of the palladium sensitised tin dioxide thin film sensors was evaluated in air inside the same closed quartz tube furnace as a function of the operating temperature (150–300°C) for a fixed concentration (3 vol%) of hydrogen gas with nitrogen as the carrier gas. The sensor response could be recorded at an operating temperature of as low as 150°C. Maximum sensitivity of 90% was found to occur at a low temperature of only 200°C. Above this cut-off temperarure, sensitivity of the present thin film sensors was found to suffer only moderate degradation.