Wei Wei, Zhu Yong, Lin Cheng, Tian Li, Xu Zu-Wen, Nong Jin-Peng
Guang Pu Xue Yu Guang Pu Fen Xi. 2014 Apr;34(4):910-4.
It is quite urgent to need a flexible photodetector in the ultraviolet-visible-near infrared region for building a miniaturization broadband spectrometer. In the present paper, one kind of flexible black silicon doped with sulfur and fluorine was proposed and the optical absorption spectrum was investigated in broadband region. Firstly, the electronic structure, band structure and the optical absorption properties of the flexible black silicon doped with sulfur and fluoride were calculated using the first-principles pseudo potential calculations based on density-functional theory. Then, the absorption spectrum model of the flexible black silicon was built based on both the first-principles and finite domain time difference method. The results show that the cut-off wavelength has a red shift as the band gap of doped material becomes narrower. The higher the doping concentration is, the higher the optical absorption coefficient is obtained. The absorption coefficient of flexible black silicon doped with 50% sulfur is 8.3 times higher than that of 1.5% sulfur doping sample at the wavelength of 1 500 nm while the ratio turns to be 3 times when doped with 50% and 1.5% fluoride. The black silicon with small-size surface microstructure has the highest absorptance in the near-infrared region at the same doping concentration of 50%. Finally, a sample of flexible black silicon was fabricated by the femtosecond laser auto scanning system. The test results indicate that the absorptance of the sample is higher than 95% both in the ultraviolet and visible region and is fluctuated from 70% to 80% in the near-infrared region. It shows that as a novel light-absorbing material in broadband region the flexible black silicon doped with Sulfur and Fluorine has an potential application in exploring miniaturization broadband spectroscopy.
为构建小型化宽带光谱仪，急需一种在紫外 - 可见 - 近红外区域具有柔性的光电探测器。本文提出了一种掺杂硫和氟的柔性黑硅，并对其在宽带区域的光吸收光谱进行了研究。首先，基于密度泛函理论，利用第一性原理赝势计算方法计算了掺杂硫和氟的柔性黑硅的电子结构、能带结构及光吸收特性。然后，基于第一性原理和有限时域差分法建立了柔性黑硅的吸收光谱模型。结果表明，随着掺杂材料带隙变窄，截止波长发生红移。掺杂浓度越高，光吸收系数越大。在1500 nm波长处，掺杂50%硫的柔性黑硅的吸收系数比掺杂1.5%硫的样品高8.3倍，而掺杂50%和1.5%氟时，该比值变为3倍。在相同50%的掺杂浓度下，具有小尺寸表面微结构的黑硅在近红外区域具有最高的吸收率。最后，利用飞秒激光自动扫描系统制备了柔性黑硅样品。测试结果表明，该样品在紫外和可见光区域的吸收率均高于95%，在近红外区域的吸收率在70%至80%之间波动。结果表明，作为一种新型宽带光吸收材料，掺杂硫和氟的柔性黑硅在探索小型化宽带光谱学方面具有潜在应用价值。
