Studies on the Effects of Angle of Incidence on the Optical Reflecftance Properties of Silicon Nanowires Grown By Electroless Etching

Silicon nanowires (SiNW’s) arrays prepared by electroless etching method can significantly suppress light reflection across the visible spectrum [1]. The decrease in reflectivity is evidently due to optical absorption in the silicon. The nanowires scatter the incident light by reflection, refraction, and diffraction processes, and the light will interact with several nanowires until it is either absorbed by a nanowire or the substrate, or is reflected by the sample [2].  However, the Fresnel reflection predicts a large reflectance at a large angle of incidence (AOI) [3]. For effects of comparison, the reflectance versus wavelength data using visible light on SiNW’s grown by eletroless etching in three different concentrations of Hydrofluoric Acid (HF) and Silver nitrate (AgNO3) for different etching times at room temperature have been provided at different AOI values. In general, SiNW’s exhibit low reflectance over a wide range of AOI. SiNW’s etched with high concentration of AgNO3 produce low reflectance. These results are beneficial to the design and fabrication of nanowire-based optoelectronic devices.

In this experiment a Cary 100 UV-Visible Spectrometer was used for reflectance analysis and silicon (Si) wafers were dipped for 15, 30, 45 and 60 minutes at room in an electroless solution prepared in a petri dish containing silver nitrate (AgNO₃) and hydrofluoric acid (HF) [4].