Fast response time alcohol gas sensor using nanocrystalline F-doped SnO2 films derived via sol–gel method

Pure and fluorine-modified tin oxide (SnO2) thin films (250–300 nm) were uniformly deposited on corning glass substrate using sol–gel technique to fabricate SnO2-based resistive sensors for ethanol detection. The characteristic properties of the multicoatings have been investigated, including their electrical conductivity and optical transparency in visible IR range. Pure SnO2 films exhibited a visible transmission of 90% compared with F-doped films (80% for low doping and 60% for high doping). F-doped SnO2 films exhibited lower resistivity (0· 12 × 10 − 4 Ω cm) compared with the pure (14·16 × 10 − 4 Ω cm) one. X-ray diffraction and scanning electron microscopy techniques were used to analyse the structure and surface morphology of the prepared films. Resistance change was studied at different temperatures (523–623 K) with metallic contacts of silver in air and in presence of different ethanol vapour concentrations. Comparative gas-sensing results revealed that the prepared F-doped SnO2 sensor exhibited the lowest response and recovery times of 10 and 13 s, respectively whereas that of pure SnO2 gas sensor, 32 and 65 s, respectively. The maximum sensitivities of both gas sensors were obtained at 623 K.