Hydrogen sensors made of undoped and Pt-doped SnO₂ nanowires

Tin oxide (SnO₂) nanowires with a tetragonal structure were formed on oxidized Si substrates by thermal evaporation of tin grains at 900 °C. The morphology, crystal structure, and H₂ gas sensing properties of undoped and Pt-doped SnO₂ nanowires were investigated. SnO₂ nanowires were approximately 30-200 nm in diameter and several tens of micrometers in length. Gas sensors made of undoped, 0.8 wt% Pt-doped, and 2 wt% Pt-doped SnO₂ nanowires showed a reversible response to H₂ at an operating temperature of RT-300 °C. The sensitivity increased with increasing H₂ concentration. The highest sensitivity of 118 was obtained for 2 wt% Pt-doped SnO₂ nanowire sensor to 1000 ppm H₂ at an operating temperature of 100 °C. The gas sensing properties of Pt-doped and Pd-doped SnO₂ nanowires were also investigated to compare the effect of impurity doping. The results demonstrated that impurity doping improved the sensitivity and lowered the operating temperature at which the sensitivity was maximized.