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<p>In this work, we systematically examine the influence of different illumination sources—halogen light, infrared (IR), and laser irradiation—on the photoelectrochemical etching of silicon to develop a suitable porous nanostructure for gas sensing applications. Silicon wafers were processed using light and laser illumination (halogen irradiance of approximately 150 mW/cm<sup>2</sup>, IR light at 850 nm with an intensity of about 100 mW/cm<sup>2</sup>, and laser light at 650 nm with an intensity of roughly 80 mW/cm<sup>2</sup>), with applied current densities ranging from 10 to 30 mA/cm<sup>2</sup> over a period of 12 min. Each light source exhibits different penetration depths and carrier generation efficiencies, which influence the charge carrier density at the silicon–electrolyte interface, consequently affecting pore morphology and etching rate. Structural analyses revealed that halogen light produced vertical pores with an average diameter of around 2.2 nm, as confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM,) along with a blue-shift in photoluminescence (PL) from 643 nm (IR) to 589 nm (halogen), primarily due to increased quantum confinement. Gas sensing tests revealed that halogen-etched silicon achieved the highest sensitivity to nitrogen dioxide (NO<sub>2</sub>) (24.6%) at 25 °C, with a minimum response time of 16.3 s and a recovery time of 73.3 s, outperforming conventional IR- and laser-etched samples. The novelty of this study lies in the direct link between optical penetration behavior and the controlled development of nanostructures, offering excellent control over pore size and morphology using low-cost light sources. These findings offer new insights into photonic silicon nanostructuring for high-performance, low-temperature gas sensing.</p>

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The Role of Illumination on Electrochemically Etched Silicon Nanostructures for Gas Sensing Applications

  • 期刊论文

  • 发表日期：

    2026年1月7日

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  • Zainab S. Mutar,
  • Falah A.-H. Mutlak

摘要

In this work, we systematically examine the influence of different illumination sources—halogen light, infrared (IR), and laser irradiation—on the photoelectrochemical etching of silicon to develop a suitable porous nanostructure for gas sensing applications. Silicon wafers were processed using light and laser illumination (halogen irradiance of approximately 150 mW/cm2, IR light at 850 nm with an intensity of about 100 mW/cm2, and laser light at 650 nm with an intensity of roughly 80 mW/cm2), with applied current densities ranging from 10 to 30 mA/cm2 over a period of 12 min. Each light source exhibits different penetration depths and carrier generation efficiencies, which influence the charge carrier density at the silicon–electrolyte interface, consequently affecting pore morphology and etching rate. Structural analyses revealed that halogen light produced vertical pores with an average diameter of around 2.2 nm, as confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM,) along with a blue-shift in photoluminescence (PL) from 643 nm (IR) to 589 nm (halogen), primarily due to increased quantum confinement. Gas sensing tests revealed that halogen-etched silicon achieved the highest sensitivity to nitrogen dioxide (NO2) (24.6%) at 25 °C, with a minimum response time of 16.3 s and a recovery time of 73.3 s, outperforming conventional IR- and laser-etched samples. The novelty of this study lies in the direct link between optical penetration behavior and the controlled development of nanostructures, offering excellent control over pore size and morphology using low-cost light sources. These findings offer new insights into photonic silicon nanostructuring for high-performance, low-temperature gas sensing.