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Journal of Nanomaterials
Volume 2013 (2013), Article ID 679638, 6 pages
http://dx.doi.org/10.1155/2013/679638
Research Article

Z-Contrast STEM Imaging of Long-Range Ordered Structures in Epitaxially Grown CoPt Nanoparticles

1Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
2Department of Materials Science, Tohoku University, 6-6 Aramaki, Aoba-ku, Sendai 980-8579, Japan

Received 15 March 2013; Accepted 17 May 2013

Academic Editor: Takeshi Seki

Copyright © 2013 Kazuhisa Sato et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We report on atomic structure imaging of epitaxial L10 CoPt nanoparticles using chemically sensitive high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Highly ordered nanoparticles formed by annealing at 973 K show single-variant structure with perpendicular c-axis orientation, while multivariant ordered domains are frequently observed for specimens annealed at 873 K. It was found that the (001) facets of the multivariant particles are terminated by Co atoms rather than by Pt, presumably due to the intermediate stage of atomic ordering. Coexistence of single-variant particles and multivariant particles in the same specimen film suggests that the interfacial energy between variant domains be small enough to form such structural domains in a nanoparticle as small as 4 nm in diameter.