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Shear-driven phase transformation in silicon nanowires
L Vincent1, D Djomani1, M Fakfakh1
1Centre de Nanosciences et Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N - Orsay, 91405 Orsay cedex, France.
Nanotechnology
|January 13, 2018
Summary
Silicon nanowires transform into a hexagonal 2H-allotrope via plastic deformation and shear stress relief. This unprecedented allotrope heterostructure formation offers new insights into nanoscale phase transformations in silicon.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Physics
Background:
- Silicon nanowires (Si NWs) are crucial in nanoelectronics.
- Understanding their phase transformation under stress is vital for device stability and novel applications.
- Existing knowledge primarily focuses on bulk silicon behavior.
Purpose of the Study:
- To investigate the formation of allotrope heterostructured Si NWs.
- To elucidate the mechanism of deformation-induced phase transformation in Si NWs.
- To explore the influence of temperature and axial orientation on this transformation.
Main Methods:
- Applying radial compressive stresses to Si NWs embedded in a matrix.
- Inducing plastic deformation and subsequent phase transformation.
- Analyzing the transformation using microscopy and stress-strain analysis.
- Studying the effects of varying temperature (above 500 °C) and nanowire axial orientation.
Main Results:
- Achieved unprecedented formation of allotrope heterostructured Si NWs.
- Observed a phase transformation from diamond cubic (3C) to hexagonal (2H) allotrope.
- Identified shear-stress relief in parallel shear bands on {115} planes as the driving force.
- Demonstrated a thermally activated process above 500 °C.
Conclusions:
- The study reveals a novel, shear-driven, deformation-induced phase transformation mechanism in Si NWs.
- This mechanism differs from that observed in bulk silicon.
- The findings provide a new route for studying nanoscale phase transformations in silicon.
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