黑硅的光吸收特性

The Light Absorption of Black Silicon

黑硅(飞秒激光微构造硅)具有很强的光吸收性质。用飞秒激光在不同背景气体(SF6和N2)氛围下刻蚀硅表面得到黑硅。实验发现,黑硅光吸收性质及表面形貌与刻蚀时所处不同背景气体环境(SF6和N2)密切相关。在SF6气体环境下刻蚀得到的样品,表面尖峰比较尖锐,在测量波段(0.3-2.5)的光吸收90%以上;在N2环境下刻蚀的尖峰比较钝,在近红外波段(1.1-2.5)随着波长增加,吸收比减小。不同尖峰高度的黑硅样品在红外波段的光吸收随着尖峰高度的增加呈现增强态势。黑硅镀银后波长在1.5-10微米范围内吸收比达90%,远高于镀银前的70%。从表面尖峰结构,杂质能级,结构缺陷,表面等离子体四个角度尝试性探讨了高吸收的物理机理。黑硅的高吸收光学特性,将在红外探测器,隐身技术,高效太阳能电池等方面具有很大的潜在应用前景。

Black silicon（ microstructured by femtosecond laser on silicon） performs excellent light absorption properties. Black silicon can be formed on silicon surface by femtosecond laser in the presence of ambient gases（ SF6 and N2）. The experimental results show that the light absorption properties and surface morphology are highly correlated with the etching ambient gases（ SF6 and N2）. With the presence of SF6,the sample has sharp spikes on surface and absorptance over 90% in the measured wave range（ 0. 3- 2. 5）; while with N2 as the etching ambient gas,the spikes on surface are blunt and the absorptance drops with the increase of wavelength in near- infrared wave range（ 1. 1- 2. 5）. Within the infrared wave range,the absorptance of black silicon sample increases with the increase of spike height in a wide range. Black silicon coated with silver can have the absorptance up to 90% compare to a 70% absorptance without coating in the wave range of 1. 5-10 micrometer. The high absorptance of black silicon has a complicated mechanism,and a tentative explanation of this high absorptance has been carried out from four aspects： spikes＇ structures,impurity energy level,structure defects and surface plasma. The highly absorptance optical properties of black silicon make it a promising application material in the field of infrared detectors,stealth technology,silicon solar cells and so on.