Preparation and performance of Si coating on RB-SiC mirror for surface modification

In order to manufacture reaction bonded silicon carbide(RB-SiC) mirrors of fine optical surface, 100 μm thick Si coatings were prepared by RF magnetron sputtering on RB-SiC substrates of 70 mm diameter and then polished. Tests with ZYGO surface profilometer show that the RMS surface roughness of the surface-modified RB-SiC achieves 0.496 nm. X-ray diffraction analyses reveal the polycrystalline structure of the Si coatings. Moreover, the adhesion between Si coating and RB-SiC substrate measured by direct pull-off method is more than 10.7 MPa. Therefore, the magnetron sputtered Si coating can satisfy the requirements of RB-SiC surface modification．