In situ study of size and temperature dependent brittle-to-ductile transition in single crystal silicon

Wonmo Kang, M Taher A Saif

Research output: Contribution to journalArticle

Abstract

Silicon based micro- and nanometer scale devices operating at various temperatures are ubiquitous today. However, thermo-mechanical properties of silicon at the small scale and their underlying mechanisms remain elusive. The brittle-to-ductile transition (BDT) is one such property relevant to these devises. Materials can be brittle or ductile depending on temperature. The BDT occurs over a small temperature range. For bulk silicon, the BDT is about 545 °C. It is speculated that the BDT temperature of silicon may decrease with size at the nanoscale. However, recent experimental and computational studies have provided inconclusive evidence, and are often contradictory. Potential reasons for the controversy might originate from the lack of an in situ methodology that allows variation of both temperature and sample size. This controversy is resolved in the present study by carrying out in situ thermo-mechanical bending tests on single crystal silicon samples with concurrent control of these two key parameters. It is unambiguously shown that the BDT temperature reduces with sample size. For example, the BDT temperature decreases to 293 °C for a sample size 720 nm. A mechanism-based model is proposed to interpret the experimental observations. In situ thermo-mechanical bending tests on single crystal silicon samples are performed with concurrent control of sample size (from 720 nm to 8.7 μm) and temperature (room temperature to 375 °C) using a SiC-based MEMS stage. This study unambiguously shows that the brittle-to-ductile transition temperature reduces with sample size. To interpret the experimental observations, a mechanism-based model is proposed.

Original languageEnglish (US)
Pages (from-to)713-719
Number of pages7
JournalAdvanced Functional Materials
Volume23
Issue number6
DOIs
StatePublished - Feb 11 2013

Keywords

  • electron microscopy
  • in situ thermomechanical test
  • silicon
  • size effect

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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