研究目的
Investigating the structure and optical absorption of silicon coated with a chromium film after femtosecond laser irradiation to extend the absorption bandgap of crystalline Si to the infrared region.
研究成果
Cr-doped Si irradiated by fs laser pulses shows enhanced absorptance, especially below the bandgap of Si, with samples produced at lower fluences exhibiting better thermal stability. The study demonstrates the potential for applications in infrared detection, with the crystal quality of laser-irradiated layers improving after thermal annealing.
研究不足
The study focuses on the effects of femtosecond laser irradiation on silicon coated with chromium films, with specific attention to the absorptance below the Si bandgap and thermal stability. The limitations include the specific conditions of laser fluence and the focus on chromium as the dopant.
1：Experimental Design and Method Selection:
The study used femtosecond laser pulses to irradiate silicon coated with chromium films at different fluence values to produce microstructured surfaces. The absorptance dependence on laser fluence and thermal annealing was investigated.
2：Sample Selection and Data Sources:
High purity metal Cr thin films were deposited onto n-Si (111) surfaces using a Radio-Frequency magnetron sputtering apparatus.
3：List of Experimental Equipment and Materials:
Equipment included a titanium (Ti):sapphire fs laser amplifier, field emission scanning electron microscope (SEM), LabRAM HR Evolution Raman Spectrometer, and a spectrophotometer. Materials included high purity (
4：95%) metal Cr thin films and n-Si (111) substrates. Experimental Procedures and Operational Workflow:
The Si/Cr substrate was irradiated with fs laser pulses at a central wavelength of 800 nm, pulse duration of 100 fs, and repetition rate of
5：5 kHz. The laser fluence was varied from 23 to 90 J/cmData Analysis Methods:
The optical absorption of the samples was measured using a spectrophotometer equipped with an integrating sphere. Raman spectra were obtained to characterize the crystal structures of samples.
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