Oblique-pulse ion beams achieve cross-scale synchronized correction and ultra-smooth surfaces in ultra-thin SPO optics

Achieving sub-arcsecond resolution in next-generation X-ray telescopes like Athena requires ultra-thin Silicon Pore Optics (SPO) mirrors with exceptional surface accuracy (TTV <100 nm) and ultra-smoothness (<0.1 nm roughness). Current fabrication methods fall short: contact polishing deforms thin wafers, while non-contact ion beam figuring (IBF) struggles with selective nanoscale material removal, especially as TTV approaches 100 nm, due to global processing and inability to suppress high-frequency errors. This study proposes an oblique pulsed ion beam (OPIB) process. By precisely controlling the pulsed beam to irradiate only identified surface high-point regions, OPIB achieves highly selective, nanoscale topographic modification. This targeted approach effectively mitigates the additional material removal layers inherent to conventional global scanning methods. Furthermore, leveraging the asymmetric sputtering effect of oblique pulsed beams, the OPIB process efficiently planarizes nanoscale structures. This synergistic action ultimately yielded an atomically ultra-smooth and flat surface, characterized by a TTV of 46.7 nm and an RMS roughness of 0.081 nm. This technology provides a groundbreaking paradigm for cross-scale morphology control in high-precision ultra-thin optical components (X-ray focusing mirrors, EUV lithography masks), offering significant industrial application potential.