More nanomaths … Coexistence of wrinkles and blisters in supported graphene
Coexistence of wrinkles and blisters in supported graphene
Kuan Zhang (LaCàN, U. Politècnica de Catalunya) and Marino Arroyo (LaCàN, UPC)
During this project we examined the mechanics of bubbles in supported graphene. In experiments, graphene bubbles have been observed with different sizes and shapes. The reported radii of the circular edges of quasi-spherical bubbles range from dozens of nanometers to several microns (1). Gas released from the substrate can become trapped under the impermeable graphene sample, creating a significant pressure difference across the membrane that produces and stabilizes tense bubbles (2). The amount of gas inside the interstitial space can be used to control the size of bubbles (1). Moreover, blisters with straight edges have been observed, possibly in association with wrinkles (3). Triangular and quadrangular straight-edged bubbles have been observed and controlled by an external electric field (4). It has been shown that a small triangular bubble can generate a very large pseudo- magnetic field, demonstrating that the electronic structure of graphene can be strain engineered. Figure  (a-d) shows experimental observations of bubbles of different morphology in supported graphene samples.
The mechanics of quasi-spherical bubbles has been previously examined in detail. However, the mechanism leading to straight-edged bubbles remains unexplored, despite numerous experimental observations. Furthermore, the coexistence and interaction between wrinkles and blisters has not been investigated. In this project, we attempted to address these issues, see our simulations in Figure  (e-h) and provide a unified picture of bubbles and wrinkles in supported graphene.
Figure 1: (a-c) AFM topography scan of triangular, quadrangular and circular bubbles, (d) A representative AFM image of straight-edged bubbles coexisting with wrinkles. Our simulations on graphene bubbles with various configurations: (e) a circular bubble, (f) a quadrangular straight-edged bubble, (g) a triangular straight-edged bubble, and (h) a lenticular bubble.
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