The gas sensitivity properties of WO3 thin films have been studied for the detection of O3 gas (25-200 ppb), and NO2 (0.7-5 ppm) in the working temperature range 150-300 °C. Thin film sensors have been obtained by evaporating commercial WO3 powders on sapphire substrates provided with Pt finger type sputtered electrodes and annealing at 500 °C for different hours. The film morphology, crystalline phase and chemical composition of the sensors have been characterized through SEM, low angle XRD and XPS. The electrical response has been measured by exposing the annealed films to O3, NO2 in dry air. The 500 °C annealed for 24 hours shows the highest sensitivity to O3 at 215 °C (S = 30 at 175 ppb O3), while the highest NO2 gas sensitivity is reached at 250 °C working temperature (S = 45 at 1.7 ppm NO2). The annealing time has the effect to enhance the O3 and NO2 sensitivities.
Vacuum thermally evaporated WO3 thin film ozone sensor
CANTALINI, Carlo;SANTUCCI, Sandro;PASSACANTANDO, MAURIZIO;
1999-01-01
Abstract
The gas sensitivity properties of WO3 thin films have been studied for the detection of O3 gas (25-200 ppb), and NO2 (0.7-5 ppm) in the working temperature range 150-300 °C. Thin film sensors have been obtained by evaporating commercial WO3 powders on sapphire substrates provided with Pt finger type sputtered electrodes and annealing at 500 °C for different hours. The film morphology, crystalline phase and chemical composition of the sensors have been characterized through SEM, low angle XRD and XPS. The electrical response has been measured by exposing the annealed films to O3, NO2 in dry air. The 500 °C annealed for 24 hours shows the highest sensitivity to O3 at 215 °C (S = 30 at 175 ppb O3), while the highest NO2 gas sensitivity is reached at 250 °C working temperature (S = 45 at 1.7 ppm NO2). The annealing time has the effect to enhance the O3 and NO2 sensitivities.Pubblicazioni consigliate
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