Strong Mid-Infrared Absorption and High Crystallinity of Microstructured Silicon Formed by Femtosecond Laser Irradiation in NF_3 Atmosphere

摘要

Arrays of high-quality crystalline conical spikes were formed on silicon surface in the presence of NF_3 with femtosecond laser irradiation.The surface of the structures is smooth, and Raman scattering spectroscopy shows that few silicon polymorphs such as a-Si, Si-Ⅻ, and Si-Ⅲ were observed in the conical structures.In the mid-infrared wavelength range of 3-16 μm, the structured surface exhibits a high absorptance up to 0.8.Additionally, the absorptance of the sample remains almost unchanged after the annealing process.These properties of the structured silicon will make it a promising material for mid-infrared applications in optoelectronic fields.