Thermal and nonthermal melting of silicon exposed to femtosecond pulses of x-ray irradiation

Nikita Medvedev; Zheng Li; Beata Ziaja

doi:10.1117/12.2182765

12 May 2015 Thermal and nonthermal melting of silicon exposed to femtosecond pulses of x-ray irradiation

Nikita Medvedev, Zheng Li, Beata Ziaja

Proceedings Volume 9511, Damage to VUV, EUV, and X-ray Optics V; 95110I (2015) https://doi.org/10.1117/12.2182765
Event: SPIE Optics + Optoelectronics, 2015, Prague, Czech Republic

Abstract

Silicon irradiated with an ultrashort laser pulse can experience two competing damage processes: the ultrafast ’nonthermal melting’ or the picoseconds ‘thermal melting’. The first one occurs if the density of excited electrons within the conduction band overcomes a certain threshold value, which leads to modification of the atomic potential energy surface and triggers a phase transition. The second one heats a material due to the electron-ion (electron-phonon) coupling, which in case of atomic temperature exceeding melting temperature also induces a phase transition. Our recently developed code XTANT (X-ray-induced Thermal And Nonthermal Transition; N. Medvedev et. al, Phys. Rev. B 91 (2015) 054113), can model both effects simultaneously. Nonadiabatic electron-ion coupling is treated within tight binding molecular dynamics model beyond the Born-Oppenheimer approximation. Two different channels of phase transition emerge at different irradiation dose: thermal melting of silicon into low-density-liquid phase occurs for deposited energies above ~0.65 eV/atom; nonthermal melting into high-density liquid takes place for doses higher than ~0.9 eV/atom. Here we discuss in detail electronic processes during such phase transitions. Evolution of the electronic structure is presented.

Citation Download Citation

Nikita Medvedev, Zheng Li, and Beata Ziaja "Thermal and nonthermal melting of silicon exposed to femtosecond pulses of x-ray irradiation", Proc. SPIE 9511, Damage to VUV, EUV, and X-ray Optics V, 95110I (12 May 2015); https://doi.org/10.1117/12.2182765

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