Fabrication of nanograined silicon by high-pressure torsion

Yoshifumi Ikoma, Kazunori Hayano, Kaveh Edalati, Katsuhiko Saito, Qixin Guo, Zenji Horita, Toshihiro Aoki, David J. Smith

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


This paper describes fabrication of Si nanograins through allotropic phase transformation by concurrent application of high pressure and intense straining using high-pressure torsion (HPT). Single-crystalline Si(100) wafers were processed by HPT under a pressure of 24 GPa at room temperature. X-ray diffraction and Raman analysis revealed that the HPT-processed samples were composed of metastable Si-III and Si-XII phases and amorphous phases in addition to the original diamond-cubic Si-I phase. It was found that nanograins formed because the Si-I diamond phase had transformed to high-pressure phases (Si-II, Si-XI, and Si-V) having metallic nature, and it then became easier to generate a high density of dislocations to form grain boundaries. The high-pressure phases were further transformed to the Si-XII and Si-III phases via the Si-II phase upon unloading and they existed as metastable phases at ambient pressure. Subsequent annealing at 873 K gave rise to reverse transformation to Si-I but with nanograin sizes. Although no appreciable photoluminescence (PL) peak was observed from the HPT-processed sample, a broad PL peak centered around 600 nm was detected from the annealed sample due to quantum confinement in the Si-I nanograins.

Original languageEnglish
Pages (from-to)6565-6569
Number of pages5
JournalJournal of Materials Science
Issue number19
Publication statusPublished - Oct 2014

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Mechanics of Materials
  • Mechanical Engineering


Dive into the research topics of 'Fabrication of nanograined silicon by high-pressure torsion'. Together they form a unique fingerprint.

Cite this