Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures

Nature routinely produces nanostructured surfaces with useful properties1,2,3,4, such as the self-cleaning lotus leaf5, the colour of the butterfly wing6, the photoreceptor in brittlestar7 and the anti-reflection observed in the moth eye8. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications9,10,11,12. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes8,13,14. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.