Adhesion toughness of multilayer graphene films

Joseph D Wood,Christopher M Harvey,Simon Wang

doi:10.1038/s41467-017-02115-w

Joseph D Wood, Christopher M Harvey + Show 1 more

Open Access

https://doi.org/10.1038/s41467-017-02115-w

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Abstract

Interface adhesion toughness between multilayer graphene films and substrates is a major concern for their integration into functional devices. Results from the circular blister test, however, display seemingly anomalous behaviour as adhesion toughness depends on number of graphene layers. Here we show that interlayer shearing and sliding near the blister crack tip, caused by the transition from membrane stretching to combined bending, stretching and through-thickness shearing, decreases fracture mode mixity GII/GI, leading to lower adhesion toughness. For silicon oxide substrate and pressure loading, mode mixity decreases from 232% for monolayer films to 130% for multilayer films, causing the adhesion toughness Gc to decrease from 0.424 J m−2 to 0.365 J m−2. The mode I and II adhesion toughnesses are found to be GIc = 0.230 J m−2 and GIIc = 0.666 J m−2, respectively. With point loading, mode mixity decreases from 741% for monolayer films to 262% for multilayer films, while the adhesion toughness Gc decreases from 0.543 J m−2 to 0.438 J m−2.

Highlights

Interface adhesion toughness between multilayer graphene films and substrates is a major concern for their integration into functional devices
By assuming the substrate to have a sinusoidal rough surface, they attempted to calculate the adhesion energy. They concluded that the large decrease in adhesion toughness from monolayer to multilayer graphene films is due to the increase in bending strain energy caused by the large increase in the bending stiffness
Note that the fracture mode mixity and the interlayer shear and sliding effect are not considered anywhere in the current analytical mechanical models[1,2,3,4,5,6,7,8,9,10] and we argue that this has caused confusion when calculating adhesion toughness

Summary

Introduction

Interface adhesion toughness between multilayer graphene films and substrates is a major concern for their integration into functional devices. Koenig et al.[1] suggested that one possible cause for the large decrease in adhesion toughness for multilayer graphene films in comparison to monolayer ones is the roughness of the substrate surface.

Results

Conclusion