Study on silicon nanopillars with ultralow broadband reflectivity via maskless reactive ion etching at room temperature

Nanostructured silicon with low surface reflectivity has important application prospects in a wide range. We fabricate crystalline silicon nanopillars with ultralow broadband reflectivity via maskless reactive ion etching at room temperature. The measurements show that the silicon nanopillars are in nano-scale diameter and micron-scale height with tip ends, which show extremely powerful antireflection capability. The silicon nanopillars with the heights of 5 μm and 7 μm demonstrate ultralow weighted average reflectivity of 0.80% and 0.40%, respectively, in a wide wavelength range of 300-1030 nm. Additional SiNx coating reduces the reflectivity to 0.09%. The two-dimensional weighted average reflectivity as function of angle of incidence and wavelength is measured, which shows low sensitivity to angle of incidence in the range of 0°-70°. The calculated wavelength dependent reflectance is in good agreement with the measured result in the range of 300-1030 nm.