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<p>Two-dimensional (2D) tin disulfide (SnS<sub>2</sub>) photodetector with interdigitated electrodes was fabricated on a sapphire substrate via a precisely controllable synthesis route. Instead of random exfoliation, SnO<sub>2</sub> thin films deposited by radiofrequency (RF) magnetron sputtering were systematically converted to layered SnS<sub>2</sub> through a localized sulfurization process. This approach enabled precise control of the active layer thickness from two to five layers, allowing for a rigorous investigation of thickness-dependent optoelectronic properties. Then, Ni/Au top electrodes were fabricated by thermal evaporation to complete the process of photodetector. Structural and optical characterizations, including transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDS), Raman spectroscopy, x-ray diffraction (XRD), and photoluminescence (PL) confirmed high-quality crystalline formation. Devices with controlled thicknesses from two to five layers were systematically investigated. After being illuminated by a Xenon lamp from 300&#xa0;nm to 650&#xa0;nm, the <i>I–V</i> curves revealed a maximum photoresponse in the 525–550&#xa0;nm band, corresponding to an estimated bandgap of 2.25–2.36&#xa0;eV. Among the devices, the three-layer SnS<sub>2</sub> achieved the best responsivity of ~3.95&#xa0;A/W, sensitivity of 11.3, detectivity of 7.5 × 10<sup>9</sup> Jones, and an external quantum efficiency (EQE) of 42.5%. This work addresses a key limitation in previous studies, where the layer-dependent photoresponse of SnS<sub>2</sub> photodetectors has been reported but lacks a systematic physical interpretation. In this study, we establish a clear correlation between the performance peak and the critical trade-off between optical absorption volume and carrier recombination dynamics. Furthermore, we identify an optimal three-layer configuration and demonstrate stable switching reproducibility with a rise time of 190&#xa0;s and a decay time of 90&#xa0;s. These findings provide a generalized and physically grounded design guideline for layer-optimized 2D SnS<sub>2</sub> photodetection platforms.</p>

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Layer-Dependent Photoresponse Optimization in Two-Dimensional SnS2 MSM Photodetectors

  • 期刊论文

  • 发表日期：

    2026年5月27日

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  • Qi-Rui Qiu,
  • Sheng-Po Chang,
  • Shoou-Jinn Chang,
  • Jone-Fang Chen,
  • Wei-Chih Lai

摘要

Two-dimensional (2D) tin disulfide (SnS2) photodetector with interdigitated electrodes was fabricated on a sapphire substrate via a precisely controllable synthesis route. Instead of random exfoliation, SnO2 thin films deposited by radiofrequency (RF) magnetron sputtering were systematically converted to layered SnS2 through a localized sulfurization process. This approach enabled precise control of the active layer thickness from two to five layers, allowing for a rigorous investigation of thickness-dependent optoelectronic properties. Then, Ni/Au top electrodes were fabricated by thermal evaporation to complete the process of photodetector. Structural and optical characterizations, including transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDS), Raman spectroscopy, x-ray diffraction (XRD), and photoluminescence (PL) confirmed high-quality crystalline formation. Devices with controlled thicknesses from two to five layers were systematically investigated. After being illuminated by a Xenon lamp from 300 nm to 650 nm, the I–V curves revealed a maximum photoresponse in the 525–550 nm band, corresponding to an estimated bandgap of 2.25–2.36 eV. Among the devices, the three-layer SnS2 achieved the best responsivity of ~3.95 A/W, sensitivity of 11.3, detectivity of 7.5 × 109 Jones, and an external quantum efficiency (EQE) of 42.5%. This work addresses a key limitation in previous studies, where the layer-dependent photoresponse of SnS2 photodetectors has been reported but lacks a systematic physical interpretation. In this study, we establish a clear correlation between the performance peak and the critical trade-off between optical absorption volume and carrier recombination dynamics. Furthermore, we identify an optimal three-layer configuration and demonstrate stable switching reproducibility with a rise time of 190 s and a decay time of 90 s. These findings provide a generalized and physically grounded design guideline for layer-optimized 2D SnS2 photodetection platforms.