Holey Substrate-Directed Strain Patterning in Bilayer MoS₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) layered materials exhibit strain-tunable properties crucial for electronic applications.
• Controlling and patterning strain in 2D materials is challenging but essential for device engineering.

Purpose of the Study:

• To develop a method for spontaneously inducing predictable strain patterns in 2D materials.
• To investigate the formation of 3D topography and strain in 2D materials on patterned substrates.

Main Methods:

• Float-capturing ultrathin flakes of single-crystal 2H-molybdenum disulfide (MoS2) on amorphous, holey silicon nitride substrates.
• Utilizing transmission electron microscopy (TEM) imaging and diffraction, alongside atomic force microscopy (AFM) for topographic mapping.
• Employing atomistic and image simulations to predict strain pattern formation.

Main Results:

• Formation of highly symmetric, high-fidelity strain patterns in MoS2 flakes conforming to substrate topography.
• Observation of symmetric, out-of-plane bowl-like deformation up to 35 nm and in-plane isotropic tensile strains up to 1.8%.
• Accurate prediction of spontaneous strain pattern formation using simulations with van der Waals forces and substrate topography as inputs.

Conclusions:

• Predictable strain patterns and 3D topography can be spontaneously induced in 2D materials by capturing them on bare, holey substrates.
• This technique offers a new pathway for precisely controlling strain in 2D materials.
• Enables advanced electron scattering studies of substrate-free, precisely aligned strained regions in 2D materials.