Interlayer Slip Engineering Induces Unexpected Out-Of-Plane Piezoelectricity in Group-VA Nanosheets

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Piezoelectricity is typically absent in centrosymmetric materials like β-phase bismuth (Bi) and antimony (Sb) due to symmetry constraints.
• Conventional 2D piezoelectric materials are limited in their applications.

Purpose of the Study:

• To investigate and demonstrate previously unreported out-of-plane piezoelectricity in β-phase Bi and Sb nanosheets.
• To explore a new mechanism for inducing piezoelectricity in non-piezoelectric 2D materials.

Main Methods:

• Synthesis of β-phase Bi and Sb nanosheets via electrochemical exfoliation.
• Characterization using Piezoresponse Force Microscopy (PFM) to measure piezoelectric response.
• Second-Harmonic Generation (SHG) measurements to confirm symmetry breaking.
• Density Functional Theory (DFT) calculations to understand the underlying mechanism.

Main Results:

• Experimental confirmation of significant out-of-plane piezoelectricity in β-phase Bi and Sb nanosheets.
• Measured longitudinal piezoelectric coefficient (d₃₃) up to ~200 pm V^-1, competitive with established 2D piezoelectrics.
• DFT calculations revealed that interlayer slip during exfoliation induces an AA- to AB-stacking transition, breaking inversion symmetry.

Conclusions:

• Interlayer stacking-mode engineering is a viable universal mechanism to induce piezoelectricity in non-piezoelectric 2D materials.
• This discovery opens avenues for developing novel nanoscale electromechanical and piezocatalytic devices utilizing Bi and Sb nanosheets.