The light-enhanced NO2 sensing properties of porous silicon gas sensors at room temperature

The NO₂ gas sensing behavior of porous silicon (PS) is studied at room temperature with and without ultraviolet (UV) light radiation. The PS layer is fabricated by electrochemical etching in an HF-based solution on a p⁺-type silicon substrate. Then, Pt electrodes are deposited on the surface of the PS to obtain the PS gas sensor. The NO₂ sensing properties of the PS with different porosities are investigated under UV light radiation at room temperature. The measurement results show that the PS gas sensor has a much higher response sensitivity and faster response--recovery characteristics than NO₂ under the illumination. The sensitivity of the PS sample with the largest porosity to 1 ppm NO₂ is 9.9 with UV light radiation, while it is 2.4 without UV light radiation. We find that the ability to absorb UV light is enhanced with the increase in porosity. The PS sample with the highest porosity has a larger change than the other samples. Therefore, the effect of UV radiation on the NO₂ sensing properties of PS is closely related to the porosity.