多层纳米微结构的制备与陷光机理研究

采用电化学腐蚀方法在单晶硅片表面制备了折射率渐变的多层纳米微结构。用扫描电镜和UV-VIS-NIR分光光度计分别分析了多层纳米微结构的表面形貌和反射率。研究了腐蚀电流密度和腐蚀时间对微结构减反射性能的影响并分析了多层纳米微结构的陷光机理。结果表明:硅片表面的纳米孔径随着腐蚀电流密度和腐蚀时间增加而增大,初始腐蚀电流密度为12.25mA/cm2和腐蚀时间为2s时,表面最大的纳米孔径为30nm,在400nm～800nm的可见光波长范围内的反射率为3.4%,在200 nm～2000nm的宽波长范围内反射率仅为5.8%,远小于常规金字塔对应的反射率。这种宽波段范围的低反射率来源于多层纳米微结构中邻层相差很小的等效折射率。

Study on Fabrication and Light Trapping Mechanism of Multilayer Nanostructure

A gradient-index multilayer nanostructure was obtained on silicon surface by electrochemical etching in this paper. The morphologies and reflectance of multilayer nanostructure were tested by scanning electron microscope and UV-VIS-NIR spectrophotometer, respectively. The influences of corrosion time and current density on the reflectance of the silicon surface were studied. And the light trapping mechanism of multilayer nanostructure was discussed. The results show that the diameter of nanopores increases with increasing corrosion current density and corrosion time. When corrosion current density and time were 12.25 mA/cm2 and 2 s respectively, the maximum diameter of nanopores is about 30 nm. An average reflectance of 3.4% between 400 nm and 800 nm was obtained in the sample, and the surface reflectivity between 200 and 2000 nm is only 5.8%, which is much smaller than that of silicon surface with pyramid texture. The low reflectivity results from the small difference of refractive index in the neighbouring layer of the samples.