Simulations of laser-induced dynamics in free-standing thin silicon films
Femtosecond-laser pulses can induce tremendous structural changes in materials. In most cases these changes are accompanied by a structural reconstruction of the materials’ surface. So far, ab initio methods were not able to simulate laser-excited materials with open boundary conditions, like, films due to technical problems. We have succeeded in overcoming these problems and in performing molecular dynamics simulations of laser-excited thin silicon films. This new stage of ab initio molecular dynamics simulations will influence widely the field of laser-excited solids in both, experiment and theory, allowing to address questions that were unreachable before. Our results indicate that for a moderate excitation strength a breathing mode is induced in the whole film in the direction perpendicular to the surface. In the high intensity regime we predict the time-evolution of experimentally accessible structure factor intensities dependent on the depth into the surface. The results indicate that the surfaces are more resilient than the film center to the femtosecond-laser excitation.
We acknowledge gratefully the financial support of the Deutsche Forschungsgemeinschaft through the project GA465/16-1 and GA465/18-1. The needed computations were performed at the Lichtenberg High Performance Computer of the Technical University Darmstadt.