Self-organized twist-heterostructures via aligned van der Waals epitaxy and solid-state transformations

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Vertical van der Waals (vdW) heterostructures are crucial for band-structure engineering using moiré superlattices.
• Current methods like micromechanical stacking limit scalable synthesis of twisted heterostructures.

Purpose of the Study:

• To develop a scalable, direct synthesis method for twisted 2D vdW heterostructures.
• To control interlayer twist angles in heterostructures for novel electronic properties.

Main Methods:

• Growing ultrathin orthorhombic tin sulfide (SnS) on trigonal tin disulfide (SnS₂) with controlled azimuthal alignment.
• Utilizing excess sulfur to induce spontaneous transformation of SnS to SnS₂, defining the twist angle.
• Employing microscopy to observe growth and nucleation dynamics.

Main Results:

• Demonstrated vdW epitaxy enabling azimuthal order between non-isotypic 2D crystals (SnS on SnS₂).
• Achieved a 30° twist angle in SnS₂/SnS₂ heterostructures, dictated by the intermediate SnS layer.
• Observed preferential nucleation on twisted domains, enabling layer-by-layer twist control.

Conclusions:

• A novel bottom-up strategy for scalable synthesis of twisted 2D heterostructures is established.
• The method allows precise control over interlayer twist angles, essential for band-structure engineering.
• This approach opens pathways for creating complex twisted stacks with tailored electronic properties.