Directionally Locked Heteroepitaxy with a Structurally Modulated van der Waals Material

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Heteroepitaxy of symmetry-mismatched layers typically requires surface treatments due to weak van der Waals (vdW) bonding.
• This limits the combination of materials for designing novel heterostructures.

Purpose of the Study:

• To investigate how lattice instabilities in a vdW substrate influence the growth and alignment of mismatched epilayers.
• To explore a new method for achieving precise interlayer registry in heterostructures.

Main Methods:

• In situ heating transmission electron microscopy (TEM) to observe growth dynamics.
• Phonon calculations to identify lattice instabilities.
• Temperature-dependent selected area electron diffraction (SAED) to analyze structural alignment.

Main Results:

• A Peierls-like lattice instability was observed in TaCo2Te2 around 523 K.
• Thermally induced surface diffusion and lateral growth of Co_xTe_y epilayers were confirmed.
• The Co_xTe_y/TaCo2Te2 heterointerface achieved directional locking, aligning lattice mismatch along the substrate's instability axis.

Conclusions:

• Lattice instabilities in vdW substrates can be leveraged to control epitaxy and achieve precise alignment of symmetry-mismatched materials.
• This approach enables one-dimensional lattice incommensuration and stabilizes heterointerfaces at elevated temperatures.
• Findings expand material diversity for designing multidimensional heterostructures.