Silicon Nanotips Antireflection Surface for Micro Sun Sensor

We have developed a new technique to fabricate antireflection surface using silicon nano-tips for use on a micro sun sensor for Mars rovers. We have achieved randomly distributed nano-tips of radius spanning from 20 nm to 100 nm and aspect ratio of ∼200 using a two-step dry etching process. The 30° specular reflectance at the target wavelength of 1 μm is only about 0.09 %, nearly three orders of magnitude lower than that of bare silicon, and the hemispherical reflectance is ∼8%. By changing the density and aspect ratio of these nanotips, the change in reflectance is demonstrated. Using surfaces covered with these nano-tips, the critical problem of ghost images that are caused by multiple internal reflections in a micro sun sensor was solved.