A novel silicon nanotips antireflection surface for the micro sun sensor

We have developed a new technique to fabricate an antireflection surface using silicon nanotips for use on a micro Sun sensor for Mars rovers. We have achieved randomly distributed nanotips of radii spanning from 20 to 100 nm and aspect ratio of similar to 200 using a two-step dry etching process. The 30 degrees specular reflectance at the target wavelength of 1 mu m is only about 0.09%, nearly 3 orders of magnitude lower than that of bare silicon, and the hemispherical reflectance is similar to 8%. When the density and aspect ratio of these nanotips are changed, a change in reflectance is demonstrated. When surfaces are 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.