Exotic silicon phases synthesized through ultrashort laser-induced microexplosion: Characterization with Raman microspectroscopy

L. A. Smillie, M. Niihori, L. Rapp, B. Haberl, J. S. Williams, J. E. Bradby, C. J. Pickard, and A. V. Rode
Phys. Rev. Materials 4, 093803 – Published 30 September 2020
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Abstract

Exotic metastable phases of silicon formed under high pressure are expected to have attractive semiconducting properties including narrow band gaps that open up novel technological applications. Confined microexplosions induced by powerful ultrashort laser pulses have been demonstrated as an advanced tool for the creation of new high-pressure phases that cannot be synthesized by other means. Tightly focused laser pulses are used to generate localized modifications inside the material structure, providing the possibility for precise controlled band-gap engineering. In this study, noninvasive Raman spectroscopy was used for analysis of laser-modified zones in silicon and to determine the metastable high-pressure phases contained. Low laser energies induced the formation of amorphous-only silicon, while higher energies led to crystalline silicon polymorphs within the modifications, albeit under considerable residual stress up to 4.5 GPa. The presence of the structurally similar r8-Si, bc8-Si, and bt8-Si phases is revealed, as well as other yet to be identified phases, and the stacking-related 9R Si polytype is evidenced, presumably stress-induced by the highly compressed laser-modified zone. The ab initio random structure searching approach is used to calculate the Raman signatures and to help identify different Si polymorphs. These findings by Raman spectroscopy from ultrashort laser-induced microexplosion sites may yield insights into the local structure and properties of new silicon metastable phases and the prospect of utilizing exotic phases for extending current applications.

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  • Received 31 March 2020
  • Revised 13 August 2020
  • Accepted 2 September 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.093803

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

L. A. Smillie1,2,*, M. Niihori2, L. Rapp1, B. Haberl3, J. S. Williams2, J. E. Bradby2, C. J. Pickard4,5, and A. V. Rode1,†

  • 1Laser Physics Centre, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
  • 2Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia
  • 3Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 4Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom
  • 5Advanced Institute for Materials Research, Tohoku University, Aoba, Sendai, 980-8577, Japan

  • *lachlan.smillie@anu.edu.au
  • andrei.rode@anu.edu.au

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Issue

Vol. 4, Iss. 9 — September 2020

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