Unraveling Diverse Stacking Sequence in CVD-Grown WSe₂ Multilayers via Electron Diffraction Polarity

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• The transition from 2D to 3D layered materials has opened new avenues for functional materials research.
• Polar layered materials with noncentrosymmetry exhibit unique properties like ferroelectricity and piezoelectricity.
• Accurately determining the layer-by-layer stacking sequence in these materials is a significant challenge.

Purpose of the Study:

• To develop a robust methodology for determining the stacking sequences in multilayer polar materials.
• To address the challenge of precisely identifying layer arrangements in materials with broken inversion symmetry.
• To correlate stacking sequences with the functional properties of polar layered materials.

Main Methods:

• Integrated analysis of multiple scattering signatures from layered atomic arrangements.
• Utilizing electron diffraction polarity, which arises from structural asymmetry.
• Demonstration on chemical vapor deposition (CVD)-grown WSe2 multilayers.

Main Results:

• Successfully identified diverse stacking scenarios in WSe2 multilayers, including mixed antiparallel/parallel arrangements and spiral structures with stacking faults.
• Validated the technique using transmission electron microscopy (TEM), Kelvin probe force microscopy (KPFM), and low-frequency Raman spectroscopy.
• Confirmed the reliability of the diffraction polarity-based technique in correlating stacking sequence with material properties.

Conclusions:

• The developed methodology provides a critical tool for probing polar layered materials.
• This technique is broadly applicable to layered materials with broken inversion symmetry, including complex moiré systems.
• Enables automatic stacking determination, advancing research in ferroelectricity, optoelectronics, and spintronics.