Direct observation of atomic-level fractal structure in a metallic glass membrane

HY Jiang and JY Xu and QH Zhang and Q Yu and LQ Shen and M Liu and YT Sun and CR Cao and D Su and HY Bai and S Meng and BA Sun and L Gu and WH Wang, SCIENCE BULLETIN, 66, 1312-1318 (2021).

DOI: 10.1016/j.scib.2021.02.020

Determination and conceptualization of atomic structures of metallic glasses or amorphous alloys remain a grand challenge. Structural models proposed for bulk metallic glasses are still controversial owing to experimental difficulties in directly imaging the atom positions in three-dimensional structures. With the advanced atomic-resolution imaging, here we directly observed the atomic arrangements in atomically thin metallic glassy membranes obtained by vapor deposition. The atomic packing in the amorphous membrane is shown to have a fractal characteristic, with the fractal dimension depending on the atomic density. Locally, the atomic configuration for the metallic glass membrane is composed of many types of polygons with the bonding angles concentrated on 45 degrees-55 degrees. The fractal atomic structure is consistent with the analysis by the percolation theory, and may account for the enhanced relaxation dynamics and the easiness of glass transition as reported for the thin metallic glassy films or glassy surface. (c) 2021 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

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