2011年6月
Nanovoid formation by change in amorphous structure through the annealing of amorphous Al2O3 thin films
ACTA MATERIALIA
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- 巻
- 59
- 号
- 11
- 開始ページ
- 4631
- 終了ページ
- 4640
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1016/j.actamat.2011.04.008
- 出版者・発行元
- PERGAMON-ELSEVIER SCIENCE LTD
The formation mechanism of a high density of nanovoids by annealing amorphous Al2O3 thin films prepared by an electron beam deposition method was investigated. Transmission electron microscopy observations revealed that nanovoids similar to 1-2 nm in size were formed by annealing amorphous Al2O3 thin films at 973 K for 1-12 h, where the amorphous state was retained. The elastic stiffness, measured by a picosecond laser ultrasound method, and the density, measured by X-ray reflectivity, increased drastically after the annealing process, despite nanovoid formation. These increases indicate a change in the amorphous structure during the annealing process. Molecular dynamics simulations indicated that an increase in stable AlO6 basic units and the change in the ring distribution lead to a drastic increase in both the elastic stiffness and the density. It is probable that a pre-annealed Al2O3 amorphous film consists of unstable low-density regions containing a low fraction of stable AlO6 units and stable high-density regions containing a high fraction of stable AlO6 units. Thus, local density growth in the unstable low-density regions during annealing leads to nanovoid formation (i.e., local volume shrinkage). (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
- リンク情報
- ID情報
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- DOI : 10.1016/j.actamat.2011.04.008
- ISSN : 1359-6454
- Web of Science ID : WOS:000291567900037