Damage in solids irradiated by a single shot of XUV free-electron laser: Irreversible changes investigated using X-ray microdiffraction, atomic force microscopy and Nomarski optical microscopy

The article presents preliminary investigation results on the near-surface damage produced by single pulses of XUV free-electron laser in the amorphous α-SiO2, the monocrystalline silicon and the epitaxial films of gold. The irradiation was delivered with single pulses of only 25 fs at a wavelength of 32.5 nm and of energy up to 10 μJ. Structural modifications induced by irradiation were characterized by X-ray microdiffraction, as well as by the AFM and optical microscopy. Ablation craters of well-defined edges with smooth interiors and outer embankments surrounding the crater edges were found in the materials. Polycrystalline phases were revealed in Si and Au film samples, in the embankments and in central parts of some craters. In α-SiO2, a diffraction pattern typical of an amorphous material was observed without any traces of irradiation-initiated crystallization. A step-like, complete removal of gold film was evidenced inside craters, with only small gold residues in central part of craters exposed to higher fluences.