Abstract
Silicon has several technologically promising allotropes that are formed via high-pressure synthesis. One of these phases (hd) has been predicted to have a direct band gap under tensile strain, whereas other (r8 and bc8) phases are predicted to have narrow band gaps and good absorption across the solar spectrum. Pure volumes of these phases cannot be made using conventional nanowire growth techniques. In this work, Si nanowires were compressed up to ∼20 GPa and then decompressed using a diamond anvil cell in the temperature range of 25–165 °C. It was found that at intermediate temperatures, near-phase-pure bc8-Si nanowires were produced, whereas amorphous Si (a-Si) dominated at lower temperatures, and a direct transformation to the diamond cubic phase (dc-Si) occurred at higher temperatures under compression. Thus this study has opened up a new pressure–temperature pathway for the synthesis of novel Si nanowires consisting of designed phase components with transformative properties.
Highlights
Silicon has several technologically promising allotropes that are formed via high-pressure synthesis
The hd-Si phase is reported to be an indirect band gap (∼0.6 eV) semiconductor,[6] but under more than ∼4% tensile strain, its band gap is predicted to become direct,[7] and it is a promising candidate for a range of novel Si devices
All of these phases can be accessed via high-pressure synthesis; creating pure structures of these phases from bulk material is not possible and is difficult on the nanoscale due to amorphous Si (a-Si) being the dominant end phase.[8,9]
Summary
L.Q.H., A.L., J.E.B., and J.S.W. conceived the idea for this research. L.Q.H. performed the diamond anvil cell experiments and XRD measurements under the supervision of G.S. and in discussion with B.H. D.A.C. performed the transmission electron microscopy with L.Q.H. All authors contributed to the discussion and preparation of the manuscript. Notes The authors declare no competing financial interest
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
