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

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. The findings of this study by Raman spectroscopy from ultrashort laser-induced microexplosionmore » 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.« less

Authors:

Smillie, Lachlan ^[1]; Niihori, M.  ^[1];

• Search DOE PAGES for author "Niihori, M."
• Search DOE PAGES for ORCID "0000-0001-7701-4660"

Rapp, Ludovic ^[1]; Haberl, Bianca  ^[2];

• Search DOE PAGES for author "Haberl, Bianca"
• Search DOE PAGES for ORCID "0000-0002-7391-6031"

Williams, James S. ^[1]; Bradby, Jodie E. ^[1]; Pickard, Chris J. ^[3]; Rode, Andrei V. ^[1]

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+ Show Author Affiliations

1. Australian National Univ., Canberra, ACT (Australia)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Univ. College London (United Kingdom); Tohoku Univ., Sendai (Japan)

Publication Date:

Wed Sep 30 00:00:00 EDT 2020

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS) and High Flux Isotope Reactor (HFIR)

Sponsoring Org.:

Australian Research Council (ARC); USDOE Office of Science (SC); Royal Society

OSTI Identifier:

1671420

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review Materials

Additional Journal Information:

Journal Volume: 4; Journal Issue: 9; Journal ID: ISSN 2475-9953

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE