Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 80: Challenges in semiconductor theory
HL 80.5: Vortrag
Donnerstag, 19. März 2015, 16:00–16:15, EW 015
Atomistic-continuum modeling of short laser pulse melting of Si targets — •Vladimir P. Lipp1,2, Baerbel Rethfeld2, Martin E. Garcia1, and Dmitry S. Ivanov1,2 — 1University of Kassel, Kassel, Germany — 2Technical University of Kaiserslautern, Kaiserslautern, Germany
We present an atomistic-continuum model to simulate ultrashort laser-induced melting processes in semiconductor solids on the example of silicon. The kinetics of transient non-equilibrium phase transition mechanisms is addressed with a Molecular Dynamics method at atomic level, whereas the laser light absorption, strong generated electron-phonon non-equilibrium, fast diffusion of and heat conduction due to photo-excited free carriers are accounted for in the continuum. We give a description of the model, which is then applied to study the mechanism of short laser pulse melting of free standing Si films. The effect of laser-induced pressure and temperature of the lattice on the melting kinetics is investigated. Two competing melting mechanisms, heterogeneous and homogeneous, were identified. Apart of classical heterogeneous melting mechanism, the nucleation of the liquid phase homogeneously inside the material significantly contributes to the melting process. The threshold fluence value, at which homogeneous nucleation of liquid starts contributing to the classical heterogeneous propagation of the solid-liquid interface, is found from the series of simulations at different laser input fluences. On the example of Si, the laser melting kinetics of semiconductors was found to be noticeably different from that of metals with fcc crystal structure.