Femtosecond laser induced structural dynamics and melting of Cu (111) single crystal. An ultrafast time-resolved x-ray diffraction study

TL;DR

This study uses ultrafast x-ray diffraction to observe femtosecond laser-induced structural dynamics and melting in a Cu (111) single crystal, revealing thermal phase transition processes and coherent phonon behavior.

Contribution

It provides the first real-time ultrafast observation of laser-induced melting and lattice dynamics in Cu (111) crystals using time-resolved x-ray diffraction.

Findings

Lattice contraction due to blast force at low fluence

Observation of coherent acoustic phonons with ~69 ps period

Real-time detection of melting, annealing, and recrystallization processes

Abstract

Femtosecond, 8.04 KeV x-ray pulses are used to probe the lattice dynamics of 150 nm Cu (111) single crystal on mica substrate irradiated with 400 nm, 100 fs laser pulses. For pump fluencies below the damage and melting threshold, we observed lattice contraction due to the formation of a blast force, and coherent acoustic phonons with a period of ~69 ps. At larger pump fluence, solid to liquid phase transition, annealing, and recrystallization were measured in real time by monitoring the intensity evolution of the probing fs x-ray rocking curves and agreed with theoretical simulation results. The experimental data suggest the melting process is a purely thermal phase transition. This study provides, in real time, an ultrafast time-resolved detailed description of the significant processes that occurs as a result of a femtosecond light-pulse interacts with the Cu (111) crystal surface.