Effect of ion beam etching on the surface roughness of bare and silicon covered beryllium

In the paper is studied the main aspects of using ion-beam etching for finish polishing. It is found that 400 eV is the optimal energy for neon ion etching ensuring slight surface roughness smoothing in the range of incidence angles of ± 40°. The deposition of 200 nm amorphous silicon films onto beryllium and their subsequent etching with the 800 eV argon ions improve the effective surface roughness integrated across the range of the spatial frequencies of 0.025-60 μm-1, from σeff=1.37 nm down to σeff=0.29 nm. The effectiveness of the smoothing technology for x-ray applications, confirmed by the results of the study the reflective properties of the Mo/Si mirrors deposited on the substrate. The reflectivity at a wavelength of 13.5 nm increased from 2% for the substrates with the surface roughness of σeff=2.3 nm (the roughness value corresponds to the as-prepared bulk Be substrates and is taken from the literature) up to 67.5% after the smoothing technology.