Infrared Absorption of Femtosecond Laser Textured Silicon Under Vacuum

Chalcogen-doped microstructural silicon irradiated by femtosecond laser has high near-uniform absorption on a broad spectrum, but the factors leading to infrared absorption are complex and remain an open problem. To clarify the origin of infrared absorption besides hyperdoped Chalcogen atoms, micros...

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Bibliographic Details
Published in:IEEE photonics technology letters 2015-07, Vol.27 (14), p.1481-1484
Main Authors: Li, Chun-Hao, Zhao, Ji-Hong, Chen, Qi-Dai, Feng, Jing, Zheng, Wei-Tao, Sun, Hong-Bo
Format: Article
Language:English
Subjects:
Absorption
Annealing
femtosecond laser
infrared absorption
Lasers
Silicon
structural defects
Surface morphology
Surface treatment
Ultrafast optics
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Summary:Chalcogen-doped microstructural silicon irradiated by femtosecond laser has high near-uniform absorption on a broad spectrum, but the factors leading to infrared absorption are complex and remain an open problem. To clarify the origin of infrared absorption besides hyperdoped Chalcogen atoms, microstructural silicon is fabricated by femtosecond laser under vacuum condition. The relationship between infrared absorption and as-formed new phases (amorphous silicon: α-Si and nanocrystal silicon) is established. It indicates that the infrared absorption is caused by defects related to Urbach states from α-Si or nanocrystal Si, and these metastable defects disappeared after a thermal annealing process. From the absorption spectrum of microstructural silicon after etching at different times, it could be figured out that the Urbach states exist in both the surface and subsurface regions of black silicon at a depth of about 2.4 μm.
ISSN:1041-1135
1941-0174
DOI:10.1109/LPT.2015.2425953