Inversion Domain Boundary Induced Stacking and Bandstructure Diversity in Bilayer MoSe₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Tuning physical properties of 2D materials via interlayer rotation and stacking is established.
• Existing heterostructure methods with varied stacking obscure the role of specific stacking orders.
• Need for precise control over stacking in 2D materials for property manipulation.

Purpose of the Study:

• To introduce and investigate uncommon fractional lattice translations in MoSe2 homobilayers.
• To reveal the intrinsic role of specific stacking orders on the physical properties of 2D materials.
• To establish a method for creating diverse, large-area, uniform stacking sequences in 2D homobilayers.

Main Methods:

• Molecular-beam epitaxy growth of MoSe2 homobilayers.
• Introduction of inversion-domain boundaries to induce fractional lattice translations.
• Scanning transmission electron microscopy (STEM) for observing stacking orders.
• Density functional theory (DFT) for detailed geometric identification.
• Scanning tunneling spectroscopy (STS) for measuring electronic properties.

Main Results:

• Observed low-symmetry stacking orders induced by inversion-domain boundaries.
• Identified diverse, large-area, and uniform stacking sequences.
• Revealed a linear relationship between interlayer distance and stacking energy.
• Demonstrated stacking-dependent bandgaps and valence band tail states at Γ and K points.
• Observed varied energy alignments of valence states influenced by stacking.

Conclusions:

• Inversion-domain boundaries are effective in creating diverse stacking orders in 2D homobilayers.
• Stacking order significantly impacts electronic properties, including bandgaps and valence band states.
• This approach offers a pathway for designing 2D multilayers with tunable physical properties.