Exceptional plasticity of silicon nanobridges

Area of Science:

• Materials Science
• Nanotechnology
• Solid Mechanics

Background:

• Covalently bonded materials typically exhibit brittle fracture with limited plastic deformation.
• Understanding nanoscale plasticity is crucial for advanced material applications.
• Silicon, a model brittle material, was investigated for its potential to display plasticity at the nanoscale.

Purpose of the Study:

• To investigate the nanoscale plasticity of silicon nanocontacts at room temperature.
• To explore the mechanisms enabling large plastic deformation in silicon.
• To challenge the conventional understanding of brittle fracture in covalent materials.

Main Methods:

• Utilized a specialized experimental setup combining a transmission electron microscope and a microelectromechanical system.
• Fabricated and tested silicon nanocontacts (nanobridges) under tensile stress.
• Analyzed the deformation behavior and structural evolution of the nanocontacts.

Main Results:

• Observed exceptional plasticity in silicon nanocontacts, elongating up to twenty times their original length.
• Achieved a fivefold increase in volume during elongation, forming a wire-like structure.
• Identified stress-assisted diffusion and sliding of intergranular, amorphous-like material as key mechanisms.

Conclusions:

• Silicon nanocontacts demonstrate significant nanoscale plasticity, contradicting macroscopic brittle behavior.
• Surface diffusion plays a critical role in enabling large elongations in nanocontacts.
• The findings open new avenues for designing and utilizing brittle materials in novel ways.