4.7 Article

Segregation induced order-disorder transition in Cu(Au) surface alloys

Journal

ACTA MATERIALIA
Volume 154, Issue -, Pages 220-227

Publisher

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2018.05.040

Keywords

Surface segregation; In-situ transmission electron microscopy; Cu(Au); Order-disorder transition

Funding

  1. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-SC0001135]
  2. U.S. Department of Energy, Office of Basic Energy Sciences [DE-SC0012704]
  3. National Science Foundation [ACI-1548562]

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Using in-situ transmission electron microscopy and atomistic simulations, we report atomic-scale observations of segregation-induced structure changes in the surface and subsurface region of a Cu(Au) solid solution in both reductive and oxidative environments. In a H-2 atmosphere, Au segregation induces the formation of a two-atomic-layer thick ordered surface alloy with an L1(0) terminated surface layer. By switching to an O-2 atmosphere, the outermost surface develops into an Au-missing row reconstruction and simultaneously the second layer experiences an order-disorder transition via intralayer atomic exchanges. The chemical disordering then propagates to the outermost surface, driven by oxygen adsorption induced Cu surface segregation. This transforms the L1(0) missing-row reconstruction into a non-reconstructed, oxygenated surface. These observations provide a mechanistic detail regarding the evolution of the surface and subsurface of this alloy in response to environmental stimuli, and are relevant to a wide range of technologically relevant processes. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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