Electrostatic actuated strain engineering in monolithically integrated VLS grown silicon nanowires

Area of Science:

• Materials Science
• Nanotechnology
• Mechanical Engineering

Background:

• Individual nanowires (NWs) require precise strain application for property characterization.
• Existing methods often introduce shear stress, complicating analysis of uniaxial strain effects.
• Developing novel techniques for controlled strain engineering in nanomaterials is crucial.

Purpose of the Study:

• To fabricate and demonstrate an electrostatic actuated tensile straining test (EATEST) device for uniaxial strain application on individual suspended nanowires (NWs).
• To investigate the piezoresistivity of silicon nanowires (SiNWs) under precisely controlled uniaxial tensile strain.
• To showcase the potential of the EATEST device for various materials, geometries, and characterization techniques.

Main Methods:

• Fabrication of a MEMS device with integrated single-crystal SiNWs using silicon-on-insulator (SOI) wafers and vapor-liquid-solid (VLS) growth.
• Application of pure uniaxial tensile strain using the EATEST device, verified by scanning electron microscopy (SEM) for NW elongation.
• In situ electrical characterization combined with confocal μ-Raman microscopy for high-resolution strain measurement.

Main Results:

• Demonstrated the EATEST device's capability for pure uniaxial tensile strain application without shear components.
• Observed a giant piezoresistive effect in SiNWs, with conductivity increasing fivefold at 3% strain.
• Verified strain values using SEM and in situ Raman spectroscopy.

Conclusions:

• The EATEST device enables precise strain engineering in individual NWs, facilitating accurate piezoresistivity studies.
• The observed giant piezoresistive effect in SiNWs highlights the potential for novel electronic devices.
• Integration with Si technology platforms suggests a pathway for next-generation strain-engineered devices.