Time Resolved Study of Laser Induced Ultrafast Alloying Processes in Au/Pd Core Shell Nanorods

TL;DR

This study uses time-resolved X-ray diffraction at an X-ray free-electron laser to investigate the ultrafast alloying process in Au/Pd nanorods induced by femtosecond laser pulses, revealing threshold fluence and dynamic interdiffusion mechanisms.

Contribution

It provides the first detailed real-time visualization of laser-induced alloying in bimetallic nanorods at ultrafast timescales, uncovering the process dynamics.

Findings

Laser fluence threshold for alloying is ~48 mJ/cm2.

Formation of Au1.51Pd0.49 alloy observed.

Alloying involves a multi-step interdiffusion process.

Abstract

Femtosecond laser-induced alloying presents a novel approach to modifying bimetallic systems. Visualizing ultrafast processes during laser-induced alloying is essential to uncover fundamental mechanisms associated with phase transformations, which enables precise control over material composition and structure at the atomic level. In this study, we investigated the ultrafast dynamics of laser-induced alloying of Au/Pd core-shell nanorods using a time-resolved X-ray diffraction technique at an X-ray free-electron laser facility, capturing the structural evolution from picoseconds to microsecond timescales. We found that a laser fluence threshold of ~ 48 mJ/cm2 with 800 nm excitation is sufficient for melting and subsequent alloy formation. Above this threshold, the formation of Au1.51Pd0.49 was observed, and we found that alloying is not a single-step phenomenon; instead, it is a dynamic process involving interdiffusion.