Emergent layer stacking arrangements in c-axis confined MoTe₂.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Layer stacking order in 2D materials significantly impacts their functional properties, crucial for advanced electronic devices.
• Bulk Molybdenum Ditelluride (MoTe2) exhibits two main stacking arrangements: the Td phase (ferroelectric Weyl semimetal) and the 1T' phase (higher-order topological insulator).

Purpose of the Study:

• To investigate the layer stacking sequences in thin flakes of Molybdenum Ditelluride (MoTe2).
• To determine if thin MoTe2 flakes adopt bulk stacking arrangements or alternative sequences.

Main Methods:

• Utilized atomic-resolution scanning transmission electron microscopy (STEM) to directly visualize MoTe2 layer stacking.
• Analyzed nanoscale domains and stacking arrangements within thin MoTe2 flakes.

Main Results:

• Observed highly disordered stacking in thin MoTe2 flakes.
• Identified nanoscale domains of both 1T' and Td phases, alongside previously unobserved stacking arrangements.
• Attributed the observed disorder to intrinsic confinement effects influencing MoTe2's free energy.

Conclusions:

• Thin MoTe2 flakes exhibit complex and disordered stacking sequences, deviating from bulk structures.
• Intrinsic confinement effects play a key role in determining stacking arrangements in 2D MoTe2.
• C-axis confinement presents a potential strategy for controlling layer stacking in other 2D materials.