Surface roughness reduction in X-ray mirrors via sol–gel silica coatings

Surface roughness is a key point for all X-ray reflective optics, and is in general obtained through careful polishing and surface finishing. Here we propose a simple and inexpensive procedure to drastically reduce surface roughness: using sol–gel silica coatings. The motivation for this work is the improvement of X-ray mirrors obtained on Si substrate using micro-fabrication technology, where the usual polishing methods cannot be applied. Sol–gel silica layers dramatically reduce surface roughness and enhance the X-ray reflectivity up to acceptable values. The proof-of-principle presented in this paper can be further improved and applied to systems of different nature.