Fabrication of ordered Si nanopillar arrays for ultralow reflectivity

The reduction of surface reflectivity is an important approach to improve the performance of optical and optoelectronic devices. Herein, we greatly suppressed the reflectivity of the silicon surface by ordered silicon nanopillar arrays, which were fabricated by metal-assisted chemical etching. The average reflectivity of the silicon surface was suppressed to lower than 0.1% from 45% at the wavelength range of 250-1050 nm, and it remained below 1.2% when the incident angle changed from 0 degrees to 70 degrees. We investigated the effect of the height and diameter of the nanopillars on the reflectivity, which revealed that the reflectivity decreased with increasing height of the nanopillars, and the reflectivity peaks blue shifted with the reducing nanopillar diameter. The results indicate that the antireflection performance can be tuned by adjusting the height and diameter of nanopillars. Therefore, this method may provide an approach to reduce and tune the reflection of Si surfaces.