The Study of soft X-ray laser ablation and nano-scale surface modification of metals

Kawachi, Tetsuya; Ishino, Masahiko; Nishikino, Masaharu; Faenov, A.*; Pikuz, T.; Hasegawa, Noboru; Inogamov, N. A.*; Skobelev, I. Y.*; Fortov, V. E.*; Khohlov, V. A.*; Yamagiwa, Mitsuru

Laser ablation has many technological applications in material processing and nano-structure fabrication. The laser-induce damage of the materials has been intensively studied and its dependence upon the pulse width, the photon energy, and the fluence has come to be understood. Recently novel light sources in soft X-ray region, i.e., laser-based soft X-ray laser (SXRL) and X-FEL, become available, and the use of these light sources provide us new possibility of laser processing. SXRL interaction with materials is quite different from that of optical lasers: Dominant absorption process is photo-ionization which creates high energy photo-electrons with around 100 eV in localized surface layer of materials, and such a temperature growth increases the tensile stress which may induce the spallation of the surface layer or unexpected surface modification. In this presentation, we report an experimental and theoretical study of SXRL ablation and nano-scale surface modification of metals.