Adhesion, Stiffness, and Instability in Atomically Thin MoS₂ Bubbles

Area of Science:

• Materials Science
• Nanotechnology
• Solid Mechanics

Background:

• Molybdenum disulfide (MoS2) is a promising 2D material with diverse electronic and mechanical properties.
• Understanding the adhesion and mechanical behavior of 2D materials on substrates is crucial for device fabrication and performance.
• Existing models may not fully capture the complex delamination mechanics of 2D membranes.

Purpose of the Study:

• To quantify the work of separation and 2D Young's modulus of single and few-layer MoS2 membranes.
• To investigate the delamination mechanics of MoS2 bubbles under varying pressures.
• To identify and explain phenomena not covered by current adhesion and delamination models.

Main Methods:

• Mechanical blister test to measure the work of separation and Young's modulus.
• Controlled inflation and deflation of pressurized MoS2 bubbles on a SiO2 substrate.
• Analysis of bubble transitions between laminated and delaminated states.

Main Results:

• Measured work of separation of 220 ± 35 mJ/m² for MoS2 membranes.
• Determined the 2D Young's modulus of single-layer MoS2 to be 160 ± 40 N/m.
• Observed adhesion hysteresis, edge pinning, and snap-in transitions during bubble deflation, not predicted by prior models.

Conclusions:

• The study provides key mechanical and adhesion parameters for MoS2 membranes.
• New insights into delamination mechanics, including adhesion hysteresis, are presented.
• Results highlight the need for refined models to describe 2D material-substrate interactions.