IAD-Si coatings on RB-SiC space mirrors for ultrasmooth surfaces

Abstract

To eliminate surface limitation caused by Silicon impurity in RB-SiC space mirrors, a relatively thick Si film is deposited on well finished RB-SiC substrate by a new process-ion assisted depositing (IAD) to provide a better polishable surface. Testing results of IAD-Si properties are provided, showing that the amorphous film has great thermal shock resistance. Then, polishing experiments on 10±0.5µm thick IAD-Si layers are accomplished focusing on smoother surface. Surface figure and micro-roughness of the coating after polished reach 0.026λ RMS (λ=0.6328nm) and less than 0.5nm RMS respectively. Moreover, reflectivity of IAD-Si polished surface with reflective films increases higher than 4.5% than that of RB-SiC in 360-1100nm. High reflectivity and desirable thermal property make IAD-Si an attractive coating material for RB-SiC space mirrors.

Study on the Removal Depth of the Surface Plastic Domain of Silicon-Modified Silicon Carbide

“…Secondly, Sic has the characteristics of high hardness, so it is difficult to directly process Sic to obtain high-quality optical mirrors. In order to deal with these problems, the Sic substrate is usually processed to a certain precision, the PV value of the surface shape accuracy of the substrate surface should be controlled at 1λ (λ = 632.8 nm), the surface roughness of the substrate Ra < 5 nm, and then a dense silicon modified layer is plated on the surface [2][3][4]. This approach leverages the dual advantages of the Sic substrate and the modified silicon layer, ultimately enhancing the overall performance [5].…”