Fracture mechanism and electromechanical behavior of chemical vapor deposited graphene on flexible substrate under tension

Abstract

The electromechanical characteristics of chemical vapor deposited graphene transferred onto a polymeric substrate were investigated by conducting tensile tests in combination with electrical resistance measurement inside a scanning electron microscope. Our results showed that the unique interfacial adhesion character of the graphene/polymer substrate, where the graphene adheres to the substrate by weak van der Waals forces, gives rise to interfacial sliding in the region around the crack edge during tensile straining, causing a reduction in strain transfer from the substrate to the graphene, and this retards or restricts the growth of preformed cracks and promotes the nucleation of new cracks. Such a fracture mechanism (i.e., cracking mechanism) was closely associated with the electromechanical behavior, leading to a distinct three–stage feature, i.e., the stage I flat region, the stage II superlinear region and the stage III linear region, in the electrical resistance−strain curve. We demonstrated the validity of the suggested fracture mechanism and its correlation with the electromechanical characteristics by combining statistical analysis of the evolution of crack size distribution with strain, frictional force measurement and coupled thermal–electrical finite element analysis.