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

TL;DR

This study investigates the ultrafast melting dynamics of nanostructured platinum films induced by infrared laser pulses, using X-ray free-electron laser probing to reveal structural changes and phase transitions.

Contribution

It provides new insights into the melting process of nanostructured platinum under IR irradiation, combining experimental XFEL measurements with two-temperature model simulations.

Findings

Partial melting occurs at IR fluences above 200 mJ/cm²

Liquid phase contribution can be modeled with liquid metal scattering

Solid-state heating dynamics are characterized by two-temperature model simulations

Abstract

Understanding melting in metals is a hot topic of present research. This may be accomplished by pumping the system with infrared (IR) laser radiation, and probing it with hard X-rays produced by an X-ray Free-Electron Laser (XFEL). In this work we studied nanostructured polycrystalline thin films of platinum that were illuminated by IR radiation of increasing fluences. We characterized the structural response as well as the nucleation and propagation of the liquid phase as a function of time delay between the IR pump and X-ray probe. We observed partial melting of the samples for IR fluences higher than 200 mJ$\cdot$cm$^{-2}$. To fit the contribution of the liquid phase to the scattering pattern in platinum we applied a model of liquid metal. The two-temperature model simulations were performed to understand the solid-state fraction of the sample heating process as a function of time delay and fluence.