Two-dimensional ferroelasticity in van der Waals β'-In₂Se₃

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials possess unique mechanical properties for flexible electronics.
• Ferroelasticity, a key mechanical behavior, has been theoretically predicted in 2D materials but lacked experimental proof.

Purpose of the Study:

• To experimentally demonstrate and investigate 2D ferroelasticity in few-layer β'-In2Se3.
• To understand the origin of spontaneous strain and domain structures in 2D ferroelastic materials.
• To explore mechanical control over ferroelastic domains and their potential applications.

Main Methods:

• Atomic-resolution electron microscopy
• In situ X-ray diffraction
• Mechanical strain application

Main Results:

• Experimental confirmation of 2D ferroelasticity in exfoliated and CVD-grown β'-In2Se3.
• Identification of spontaneous strain from in-plane antiferroelectric distortion.
• Observation of three domain variants with 60° and 120° domain walls (DWs).
• Mechanical switching of ferroelastic domains achieved with ≤0.5% strain.
• Detailed analysis of domain switching mechanisms (DW propagation and nucleation).

Conclusions:

• 2D ferroelasticity is experimentally validated in β'-In2Se3, opening avenues for mechanical control.
• The findings suggest 2D ferroelasticity is prevalent in materials with anisotropic lattice distortion.
• Potential for strain and DW engineering to tune functionalities in 2D materials.