Electric, thermal, and optical properties of severely deformed Si processed by high-pressure torsion

Yoshifumi Ikoma, Kensuke Matsuda, Keigo Yoshida, Marina Takaira, Masamichi Kohno

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4 Citations (Scopus)


We report on electric, thermal, and optical properties of Si subjected to severe plastic deformation. Single-crystalline Si wafers were processed by high-pressure torsion (HPT) under a nominal pressure of 6 GPa. The HPT-processed samples consisted of metastable body-centered-cubic Si-III and rhombohedral Si-XII as well as diamond-cubic Si-I and amorphous phases. The metastable phases increased with increasing the number of anvil rotations (N). The resistivity of the single-crystalline Si (20 ω cm) increased to 50 ω cm after HPT processing for N = 10 and then it decreased to ∼0.7 ω cm when increasing N to 100. Such an increase and a subsequent decrease in resistivity were attributed to the grain refinement and the increase in the volume fraction of semimetallic Si-III, respectively. The thermal conductivity was reduced by two orders of magnitude (∼3 W m-1 K-1) after HPT processing for N ≥ 50. A weak broad photoluminescence peak originating from Si-I nanograins appeared in the visible light region after annealing at 600 °C. These results indicate that the resistivity, thermal conductivity, and photoluminescence of the HPT-processed Si strongly depend on the formation of metastable phases and grain refinement, which are induced by shear strain under high pressure.

Original languageEnglish
Article number215101
JournalJournal of Applied Physics
Issue number21
Publication statusPublished - Dec 7 2022

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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