宽 频 吸 波 微 纳 硅 结 构 的 激 光 掺 杂 与 原 位 沉 积 制 备

Objective Silicon is a widely used semiconductor material in the field of optoelectronics. However, the high surface reflectivity and wide intrinsic band gap of silicon significantly affect the performance of silicon-based optoelectronic devices. Inspired by biomimicry principles, researchers have fabricated micro/nano structures with different morphologies and sizes on the silicon surface. This has significantly improved the absorption performance in the ultraviolet-visible (UV-Vis) band. Nevertheless, due to silicon’s band gap of 1.12 eV, photons with wavelengths exceeding 1100 nm cannot be effectively absorbed. Furthermore, achieving broadband infrared absorption imposes stricter requirements on the hierarchical multiscale characteristics of micro/nano structures. Consequently, the absorption efficiency of existing micro/nano silicon structures in the infrared band is still far from meeting the requirements of practical applications. In this study, a novel method for fabricating multiscale micro/nano structures is proposed. This method can enable the collaborative manufacturing by the combination of laser doping and in-situ deposition, achieving ultra-low reflectance across the broadband ultraviolet-visible-infrared (UV-Vis-IR) range on silicon surface. Furthermore, the fabricated structures exhibit excellent optical stability and durability. This significantly broadens their potential applications in infrared photodetection, renewable energy, and aerospace technologies. Methods First, the in-situ deposition mechanism and evolution behavior of particles generated by femtosecond laser ablation were investigated. Through precise regulation of ablation particle deposition on material surfaces under femtosecond laser irradiation, micro/nano structures with tailored morphologies and dimensions were controllably formed via additive manufacturing. This approach demonstrates potential for efficient and controllable fabrication of multiscale micro/nano structures. Subsequently, the influence mechanism of sulfur doping on the photoelectric properties of silicon was elucidated. Introduction of absorption energy levels within silicon’s band gap was confirmed to enhance photon absorption. Finally, primary microstructures were fabricated via subtractive laser ablation, while secondary micro/nano composite structures were produced through controlled additive deposition. Simultaneously, sulfur-doped multiscale micro/nano structures were achieved through effective doping control in an SF₆ atmosphere. Results and Discussions The elemental composition of the multiscale micro/nano structures was characterized using energy dispersive spectroscopy (EDS). Analysis revealed that the femtosecond laser facilitated sulfur doping during silicon ablation in an SF ₆ atmosphere, with sulfur atoms constituting 1.16% of the surface composition (Fig. 7). Through optimization of laser processing parameters, pulse energy was set at 30 µJ, scanning speed at 6 mm/s, repetition rate at 50 kHz, and scan interval at 30 µm for fabricating micro/nano structure silicon samples. Optical characterization demonstrates that the structured surface exhibits an average reflectance of 2.23% across the UV-Vis-NIR spectrum (300 ‒ 2500 nm) and a reflectance below 3.39% over the entire measured bandwidth (Fig. 8). Notably, in the mid-infrared (MIR) region (2.5‒16.0 µm), the average reflectance measures merely 4.36% with an overall reflectance below 6.16% across the full test range, confirming significant broadband infrared absorption enhancement on the silicon surface (Fig. 10). The samples were subjected to mechanical impact using ultrasonic vibration. The comparison revealed that the average reflectance increase on the surface of the sulfur-doped silicon structures was 0.47%, which was less than the 1.16% increase on the surface of the non-sulfur-doped structures. This indicates that it has a higher antireflection stability performance. Furthermore, the antireflection durability of sulfur-doped multiscale micro/nano structures was further evaluated. Samples were exposed to ambient laboratory conditions (non-cleanroom). When measurement errors were excluded, the reflectance remained unchanged over time, demonstrating excellent durability of the antireflection performance (Fig. 8). Conclusions This study proposes a fabrication method for sulfur-doped multiscale micro/nano silicon structures via combined femtosecond laser doping and in-situ deposition, which enhances the broadband absorption properties of silicon materials. The in-situ deposition behavior of ablated particles under laser irradiation and the influence mechanism of sulfur doping on the photoelectric properties of silicon substrates were systematically examined. Primary microstructures were fabricated via laser ablation, while secondary micro/nano composite structures were formed by etching deposited materials. Concurrently, effective doping and component regulation were performed in an SF ₆ atmosphere, resulting in sulfur-doped multiscale micro/nano composite structures. Optical performance tests confirmed that the structured surface significantly enhances silicon’s absorption across the UV-Vis-NIR-MIR broadband spectrum. Subsequent mechanical shock vibration and durability evaluations demonstrated excellent stability in optical performance. These findings indicate that synergizing the hierarchical advantages of micro/nano composite structures regarding absorption efficiency and bandwidth with infrared absorption energy levels of sulfur^-doped silicon materials constitutes an effective approach for achieving efficient broadband absorption in silicon materials. The integrated laser doping and in-situ deposition strategy enables single-step fabrication of sulfur^-doped multiscale micro/nano structures, thereby streamlining process flows and improving processing efficiency in practical implementations.