Infrared-induced ultrafast melting of nanostructured platinum films probed by an x-ray free-electron laser

Abstract

Understanding non-equilibrium melting in metals is a topic of current interest. We investigated the solid-toliquid phase transition in platinum induced by femtosecond infrared radiation at different fluences. The evolution of the atomic structure was probed on the picoseconds timescale by x rays generated by an x-ray free-electron laser (XFEL). To analyze scattering data, we employed a model developed for liquid metals. We observed a compression field propagating into the nanostructured thin film sample, as well as partial melting for the infrared fluence of 200 mJ cm-2, corresponding to about 280 kJ kg-1 absorbed by the sample. Similar features were observed at higher infrared laser fluences. To support the interpretation of experimental findings, we performed two-temperature model simulations.