Investigation of damage induced by intense femtosecond XUV pulses in silicon crystals by means of white beam synchrotron section topography

• The vicinity of ablation craters induced by XUV FEL radiation was studied.
• Disturbed crystal lattice was found below the ablation craters.
• The evaluated depth extension was in the range of 30–100 µm.
• Approximation of droplet-like inclusion was used for numerical simulations.
• Melting and recrystallization may be responsible for observed defects.

Silicon crystalline samples were exposed to intense single pulses of XUV radiation (λ=13.5 nm) what lead to melting and ablation of the surface material. The deformation field around craters along the whole thickness of silicon wafers was observed by means of the synchrotron transmission section topography using the beam perpendicular to the surface of the sample. The geometrical shape and depth extension around craters was evaluated based on numerous, dense series of section topographs spaced by 10 µm. In the topographs we observed the direct image connected with the boundary of the crater associated with some deformation of the Kato fringes. The evaluated depth extension, different for individual craters, was in the range of 30–100 µm. The depth values were confirmed also by evaluations based on the Bragg case section topographs.It was possible to reproduce the contrast of the craters in transmission section topographs by numerical simulation based on integration of the Takagi–Taupin equations. The damage of the crystal defects connected with craters was approximated as droplet-like inclusions.