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<p>Noble metal core–shell nanoparticles hold significant potential as materials for future optoelectronic devices, such as those used in broadband and efficient photodetection. In this study, Ag@Au core–shell nanoparticles were synthesized via a well-controlled, surfactant-free pulsed laser ablation in liquid (PLAL) method, where the ablation time was systematically varied to 1, 2, and 3&#xa0;min to adjust the gold shell thickness. The aim was to systematically examine how the shell thickness influenced the optical and electrical properties, as well as the overall performance of the photodetectors. Porous silicon substrates were coated with nanoparticles, and their structure and morphology were thoroughly characterized using X- ray diffraction (Crystallite size 10. 9–65. 7&#xa0;nm), scanning electron microscopy, transmission electron microscopy (revealing uniform, spherical core–shell architectures), and UV–Vis spectroscopy (showing plasmonic enhancement and surface plasmon energy levels correlating to an optical bandgap shift from 2. 95&#xa0;eV at 1&#xa0;min to 2. 44&#xa0;eV at 3&#xa0;min due to increasing shell thickness and plasmonic effects). The device performances crafted with these nanostructures were tunable: the 1- minute gold- shelled photodetector exhibited the highest spectral responsivity (0. 235&#xa0;A/W at 550–600&#xa0;nm), detectivity (7. 68 × 10 ¹¹ cm· Hz ¹/²/w), and external quantum efficiency (EQE 0. 478), alongside the lowest noise equivalent power (NEP 1. 30 × 10⁻¹ ² W/√Hz), compared to thicker shell samples (2&#xa0;min: responsivity 0. 220&#xa0;A/W, detectivity 7. 11 × 10 ¹¹ cm· Hz ¹/²/w, EQE 0. 425; 3&#xa0;min: 0. 169&#xa0;A/W, 5. 61 × 10 ¹¹ cm· Hz ¹/²/w, EQE 0. 329) and devices made solely with Ag nanoparticles. The observed enhancement, up to 39% in responsivity and 45% (relative to the device with the thickest Au shell (3&#xa0;min)) in detectivity under the optimal thin-shell conditions, is attributed to reinforced plasmonic coupling and more efficient charge carrier dynamics facilitated by the nanoscale gold shell design. These findings offer valuable insights into how precise geometric control of nanostructures impacts device performance and present a potential, scalable, environmentally friendly route to developing advanced photodetectors, solar energy harvesters, and other sustainable optoelectronic systems.</p>

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Laser-Engineered Ag@Au Core–Shell Nanostructures: Impact of Shell Thickness on Photodetector Performance

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Yasmine H. Khadim,
  • Hussain M. Selman,
  • Uday M. Nayef,
  • Mohammed W. Muayad

摘要

Noble metal core–shell nanoparticles hold significant potential as materials for future optoelectronic devices, such as those used in broadband and efficient photodetection. In this study, Ag@Au core–shell nanoparticles were synthesized via a well-controlled, surfactant-free pulsed laser ablation in liquid (PLAL) method, where the ablation time was systematically varied to 1, 2, and 3 min to adjust the gold shell thickness. The aim was to systematically examine how the shell thickness influenced the optical and electrical properties, as well as the overall performance of the photodetectors. Porous silicon substrates were coated with nanoparticles, and their structure and morphology were thoroughly characterized using X- ray diffraction (Crystallite size 10. 9–65. 7 nm), scanning electron microscopy, transmission electron microscopy (revealing uniform, spherical core–shell architectures), and UV–Vis spectroscopy (showing plasmonic enhancement and surface plasmon energy levels correlating to an optical bandgap shift from 2. 95 eV at 1 min to 2. 44 eV at 3 min due to increasing shell thickness and plasmonic effects). The device performances crafted with these nanostructures were tunable: the 1- minute gold- shelled photodetector exhibited the highest spectral responsivity (0. 235 A/W at 550–600 nm), detectivity (7. 68 × 10 ¹¹ cm· Hz ¹/²/w), and external quantum efficiency (EQE 0. 478), alongside the lowest noise equivalent power (NEP 1. 30 × 10⁻¹ ² W/√Hz), compared to thicker shell samples (2 min: responsivity 0. 220 A/W, detectivity 7. 11 × 10 ¹¹ cm· Hz ¹/²/w, EQE 0. 425; 3 min: 0. 169 A/W, 5. 61 × 10 ¹¹ cm· Hz ¹/²/w, EQE 0. 329) and devices made solely with Ag nanoparticles. The observed enhancement, up to 39% in responsivity and 45% (relative to the device with the thickest Au shell (3 min)) in detectivity under the optimal thin-shell conditions, is attributed to reinforced plasmonic coupling and more efficient charge carrier dynamics facilitated by the nanoscale gold shell design. These findings offer valuable insights into how precise geometric control of nanostructures impacts device performance and present a potential, scalable, environmentally friendly route to developing advanced photodetectors, solar energy harvesters, and other sustainable optoelectronic systems.