Direct imaging of local atomic ordering in a Pd-Ni-P bulk metallic glass using Cs-corrected transmission electron microscopy

Akihiko Hirata, Yoshihiko Hirotsu, T. G. Nieh, Tadakatsu Ohkubo, Nobuo Tanaka

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

In amorphous alloys, crystalline atomic clusters as small as 1-2 nm are frequently observed as local lattice fringe images by high-resolution electron microscopy (HREM). These clusters can be understood as local structures of amorphous alloys corresponding to "medium-range-order (MRO)". The MRO structure can be observed only under suitable defocusing conditions of the objective lens in HREM. A clear imaging of the MRO structure is difficult in conventional TEMs, mainly due to the delocalization of the image, caused mainly by the spherical aberration of the objective lens and eventually by the chosen defocus. In the present study, we have examined MRO in a Pd-based bulk metallic glass (Pd40Ni40P20) using a high-resolution TEM (acceleration voltage 200 kV) fitted with a spherical aberration constant corrector (Cs corrector) for aberration correction. We found that when Cs was close to zero and defocus values were near the Gaussian focus, MRO regions with an FCC-Pd structure could be clearly observed with a low image disturbance. Under these conditions, the phase-contrast transfer function was understood to act as an ideal filter function, which distinctly selects specific lattice periods of the FCC-Pd clusters. The obtained atomic images of the glass structure including the FCC-Pd clusters are in good agreement with those expected from image simulation according to our amorphous structure model. In this study, we have demonstrated that the Cs-corrected HREM is a powerful tool to directly image locally ordered structures in metallic glasses.

Original languageEnglish
Pages (from-to)116-123
Number of pages8
JournalUltramicroscopy
Volume107
Issue number2-3
DOIs
Publication statusPublished - 2007 Feb 1
Externally publishedYes

Keywords

  • Amorphous alloys
  • Atomic ordering
  • C corrector
  • HREM imaging
  • Metallic glasses

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Instrumentation

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