Abstract

In this study, UV irradiation was used to improve the response of indium oxide (In2O3) used as a CO sensing material for a resistive sensor operating in a low temperature range, from 25 °C to 150 °C. Different experimental conditions have been compared, varying UV irradiation mode and sensor operating temperature. Results demonstrated that operating the sensor under continuous UV radiation did not improve the response to target gas. The most advantageous condition was obtained when the UV LED irradiated the sensor in regeneration and was turned off during CO detection. In this operating mode, the semiconductor layer showed an apparent “p-type” behavior due to the UV irradiation. Overall, the effect was an improvement of the indium oxide response at 100 °C toward low CO concentrations (from 1 to 10 ppm) that showed higher results than in the dark, which is promising to extend the detection of CO with an In2O3-based sensor in the sub-ppm range.

Highlights

  • Indium oxide is a semiconductor metal oxide (MOX) which displays very good performances when used as a sensing layer in resistive gas sensors for the detection of oxidizing gases like O3 and NO2 [1,2,3,4,5]

  • We report the results of an investigation on CO sensing properties of In2O3 under different UV irradiation modes to improve MOX response at low temperatures

  • Powder sample was characterized by X-ray powder diffraction (XRD) analysis (Bruker, D2 Phaser, Karlsruhe, Germany) in the 2θ range from 10 to 80◦ (Cu Kα1 = 1.54056 Å) and its morphology studied by Scanning Electron Microscopy SEM (Phenom ProX, Deben, Suffolk, UK)

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Summary

Introduction

Indium oxide is a semiconductor metal oxide (MOX) which displays very good performances when used as a sensing layer in resistive gas sensors for the detection of oxidizing gases like O3 and NO2 [1,2,3,4,5]. We report the results of an investigation on CO sensing properties of In2O3 under different UV irradiation modes to improve MOX response at low temperatures. Results showed that UV light generally did not improve In2O3 response at low temperatures, when used in certain conditions, the UV photons irradiation demonstrated to increase the sensor response. This demonstrates the possibility to detect sub-ppm concentrations of CO with In2O3-based sensor at a relatively low temperature without any use of additives

Sample Preparation and Characterization
Sensor Preparation and Testing
Conclusions

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