基于等效介质理论的纳米线黑硅光学特性研究

Optical Properties of Nanowires Black Silicon Based on Effective Medium Theory

为了研究不同形貌下纳米线黑硅阵列的减反射性能,文中采用金属辅助催化刻蚀法在硅基底表面制备大面积排列有序的硅纳米线,即纳米线黑硅。研究了刻蚀溶液中氧化剂的比例对其生长过程、表面形貌及光学特性的影响。通过亚波长光栅原理和等效介质理论计算了纳米阵列结构在特定波长下的抗反射性能的最佳参数,使用FDTD Solutions仿真软件系统模拟了宽光谱照射下尺寸参数对纳米线黑硅微结构阵列反射率的影响。研究结果表明:通过测试样品可见光到近红外波段(380~900 nm)的光学特性,相较于抛光硅片,表面存在纳米线黑硅阵列的硅片吸光度得到有效提升。通过改变刻蚀溶液中氧化剂的比例,可以定量地调控薄膜的吸光度。结合光学测试结果进行理论计算,能够提供纳米线黑硅衍射级次的变化规律,归一化周期T/λ比值持续增加,高阶级次的衍射光会逐渐出现。通过控制硅线周期来避免出现高级次衍射光,提升薄膜的减反射性能。

In order to study the antireflective properties of nanowires black silicon arrays with different morphology,a large area ordered silicon nanowires arrays,or nanowires black silicon arrays,were prepared on the surface of silicon substrate by metal-assisted chemical wet etching.The effects of the percentage of oxidants in the etching solution on the growth process,surface morphology and optical properties were studied.The optimal parameters of antireflective properties of nanometer array structure at specific wavelengths were calculated based on the subwavelength grating principle and effective medium theory,and the influence of size parameters on the reflectivity of the nanowires black silicon arrays under wide spectrum irradiation was simulated by an FDTD Solutions simulation software system.The results show that the absorbance of silicon wafers with nanowires black silicon arrays on the surface can be effectively improved compared with polished silicon wafers by testing the optical properties of samples from visible to near-infrared band(380~900 nm).The absorbance of films can be quantitatively regulated by changing the percentage of oxidants in the etching solution.The theoretical calculation combined with optical test results can provide the variation law of diffraction order of nanowires black silicon.As the ratio of normalized period T/λ increases continuously,the higher-order diffracted light can gradually appear.The higher-order diffracted light will be avoided by adjusting the period of silicon wires,improving antireflective properties of thin film.