Significant “smaller is softer” in amorphous silicon via irradiation-mediated surface modification

Yuecun Wang, Lin Tian, Meng Li, Zhiwei Shan

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


“Smaller is softer” is a reverse size dependence of strength, defying the “smaller is stronger” tenet. It usually results from surface-mediated displacive or diffusive deformation and is mainly found in some ultra-small-scale (below tens of nanometers) metallic materials. Here, making use of the surface modification via ion beam irradiation, we bring the “smaller is softer” into being in a covalently-bonded, hard, and brittle material-amorphous Si (a-Si) at a much larger size regime (< ∼500 nm). It is manifested as the transition from the quasi-brittle failure to the homogeneous plastic deformation as well as the decreasing yield stress with sample volume reduction at the submicron-scale regime. An analytical model of hard core/superplastic shell has been proposed to explain the artificially-controllable size-dependent softening. This surface engineering pathway via ion irradiation is not only of particular interest to tailor the strength and deformation behaviors in small-sized a-Si or other covalently-bonded amorphous solids but also of practical relevance to the utility of a-Si in microelectronics and microelectromechanical systems.
Original languageEnglish (US)
Pages (from-to)106-112
Number of pages7
JournalJournal of Materials Science and Technology
StatePublished - Jun 26 2023
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2023-07-17
Acknowledgements: The authors acknowledge the support from the National Key R&amp;D Program of China (no. 2022YFB3203600), the National Natural Science Foundation of China (no. 52272162), the China Postdoctoral Science Foundation (Nos. 2021T140535 and 2019M663696), and the Alexander von Humboldt Foundation. L.T. thanks Dr. Christoph Meyer and Prof. Vasily Moshnyaga for their help in Raman spectroscopy measurement. M.L. acknowledges the support from Prof. Xixiang Zhang and the nanofabrication core lab at King Abdullah University of Science and Technology for the nanofabrication facilities.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • Materials Chemistry
  • Polymers and Plastics
  • Mechanics of Materials
  • Metals and Alloys
  • Ceramics and Composites
  • Mechanical Engineering


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