Reduced Fracture Strength of 2D Materials Induced by Interlayer Friction.

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Two-dimensional layered materials (2DLMs) are crucial for flexible electronics and nano-electromechanical systems.
• Their mechanical properties are key to device performance, but interlayer interactions are not fully understood.
• Interlayer friction significantly impacts the mechanical behavior of 2DLMs.

Purpose of the Study:

• To investigate how interlayer friction affects the mechanical properties of few-layer (FL) WS2 and FL WSe2.
• To elucidate the relationship between interlayer interactions and the fracture strength of 2DLMs.
• To understand the influence of tip-membrane friction on measured mechanical properties.

Main Methods:

• Finite element simulations were employed to model mechanical behavior.
• Density functional theory (DFT) calculations were used to analyze interlayer sliding energies.
• Experimental mechanical testing was simulated to assess friction effects.

Main Results:

• Interlayer friction was found to reduce the fracture strength of FL WS2.
• FL WSe2 also exhibited reduced fracture strength, but to a lesser extent than WS2.
• DFT calculations confirmed differences in interlayer sliding energies between WS2 and WSe2.
• Tip-membrane friction can lead to an underestimation of Young's modulus.

Conclusions:

• Interlayer interactions, specifically friction, play a critical role in determining the mechanical properties of 2DLMs.
• The distinct interlayer sliding energies of WS2 and WSe2 explain their different responses to friction.
• Accurate characterization of 2DLMs requires consideration of interfacial effects, including interlayer friction.
• These findings are vital for designing reliable nanodevices utilizing 2DLMs.