Strong enhancement of surface diffusion by nonlinear surface acoustic waves

Maxim V. Shugaev, Anthony J. Manzo, Chengping Wu, Vladimir Yu. Zaitsev, Henry Helvajian, and Leonid V. Zhigilei
Phys. Rev. B 91, 235450 – Published 30 June 2015
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Abstract

The phenomenon of acoustic activation of surface diffusion is investigated in a combined computational and experimental study. The ability of pulsed laser-generated surface acoustic waves (SAWs) to enhance the mobility of small atomic clusters is demonstrated by directly tracking, with fluorescence microscopy, individual Au8 clusters moving on a (111) silicon substrate. A 19-fold increase in the effective diffusion coefficient is measured in room temperature experiments in the presence of SAWs generated by nanosecond pulse laser irradiation at a 100 Hz repetition rate. A strong enhancement of cluster mobility by SAWs is also observed in large-scale molecular dynamics simulations of surface diffusion of small atomic clusters. The analysis of the computational results demonstrates that the nonlinear sharpening of SAWs and the corresponding enrichment of the SAW spectra by high frequency harmonics which are capable of dynamic coupling to the cluster vibrations are responsible for the efficient acoustic activation of surface mobility in the simulations. The increase in the effective diffusion coefficient is proportional to the number of the SAW pulses passing through the diffusion region per unit time and a dramatic 4500-fold diffusion enhancement (corresponds to an equivalent temperature increase by 103K) is predicted in the simulations for 15GHz SAWs. The ability of SAWs to affect atomic-level surface processes has far-reaching implications for the design of new techniques where the acoustic energy serves as an effective substitution for thermal activation in applications where heating must be avoided or rapid switching of surface conditions is required.

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  • Received 26 September 2014
  • Revised 26 May 2015

DOI:https://doi.org/10.1103/PhysRevB.91.235450

©2015 American Physical Society

Authors & Affiliations

Maxim V. Shugaev1, Anthony J. Manzo2, Chengping Wu1, Vladimir Yu. Zaitsev1,3,4, Henry Helvajian2, and Leonid V. Zhigilei1,*

  • 1Department of Materials Science and Engineering, University of Virginia, 395 McCormik Road, Charlottesville, Virginia 22904-4745, USA
  • 2Physical Sciences Laboratories, The Aerospace Corporation, P.O. Box 92957, Los Angeles, California 90009-2957, USA
  • 3Institute of Applied Physics, Russian Academy of Sciences, Uljanova St. 46, Nizhny Novgorod, 603950, Russia
  • 4Nizhny Novgorod State University, Gagarina Avenue 23, Nizhny Novgorod, 603950, Russia

  • *lz2n@virginia.edu

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Issue

Vol. 91, Iss. 23 — 15 June 2015

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