Adhesion, Stiffness and Instability in Atomically Thin MoS2 Bubbles

TL;DR

This study measures the adhesion, stiffness, and delamination mechanics of atomically thin MoS2 membranes, revealing new insights into their stability, hysteresis effects, and mechanical properties relevant for 2D material applications.

Contribution

It provides the first direct measurements of work of separation and Young's modulus for MoS2, and uncovers novel hysteresis and transition behaviors during delamination.

Findings

Work of separation: 220 ± 35 mJ/m^2

Young's modulus: 160 ± 40 N/m

Observed adhesion hysteresis and snap-in transitions

Abstract

We measured the work of separation of single and few-layer MoS2 membranes from a SiOx substrate using a mechanical blister test, and found a value of 220 +- 35 mJ/m^2. Our measurements were also used to determine the 2D Young's modulus of a single MoS2 layer to be 160 +- 40 N/m. We then studied the delamination mechanics of pressurized MoS2 bubles, demonstrating both stable and unstable transitions between the bubbles' laminated and delaminated states as the bubbles were inflated. When they were deflated, we observed edge pinning and a snap-in transition which are not accounted for by the previously reported models. We attribute this result to adhesion hysteresis and use our results to estimate the work of adhesion of our membranes to be 42 +- 20 mJ/m^2.