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Structural dynamics of laser-irradiated gold nanofilms

Daraszewicz, SL; Giret, Y; Naruse, N; Murooka, Y; Yang, J; Duffy, DM; Shluger, AL; (2013) Structural dynamics of laser-irradiated gold nanofilms. Physical Review B , 88 (18) , Article 184101. 10.1103/PhysRevB.88.184101. Green open access

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Abstract

We performed relativistic ultrafast electron diffraction (UED) measurements of the structural dynamics of photoexcited gold nanofilms and developed an atomistic model, based on the two-temperature molecular dynamics (2T-MD) method, which allows us to make a direct comparison of the time evolutions of measured and calculated Bragg peaks. The quantitative agreement between the temporal evolutions of the experimental and theoretical Bragg peaks at all fluences suggests that the 2T-MD method provides a faithful atomistic representation of the structural evolution of photoexcited gold films. The results reveal the transition between slow heterogeneous melting at low absorbed photon fluence to rapid homogeneous melting at higher fluence and nonthermally driven melting at very high fluence. At high laser fluence, the time evolution of Bragg peaks calculated using the conventional 2T-MD model disagrees with experiment. We show that using an interatomic potential that directly depends on the electron temperature delivers a much better agreement with UED data. Finally, our ab initio calculations of phonon spectra suggest electronic bond softening, if the nanofilms can expand freely under electronic pressure, and bond hardening, if they are constrained in all three dimensions.

Type: Article
Title: Structural dynamics of laser-irradiated gold nanofilms
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevB.88.184101
Publisher version: http://dx.doi.org/10.1103/PhysRevB.88.184101
Language: English
Additional information: © 2013 American Physical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/1417431
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