Increasing the elastic modulus of graphene by controlled defect creation

Defects are often introduced to increase the stiffness of three-dimensional materials. Evidence now suggests that the elastic modulus of two-dimensional graphene sheets can also be increased by controlled defect creation. The extraordinary strength, stiffness 1 and lightness of graphene have generated great expectations of its application in flexible electronics and as a mechanical reinforcement agent. However, the presence of lattice defects, unavoidable in sheets obtained by scalable routes, might degrade its mechanical properties 2 , 3 . Here we report a systematic study on the elastic modulus and strength of graphene with a controlled density of defects. Counter-intuitively, the in-plane Young’s modulus increases with increasing defect density up to almost twice the initial value for a vacancy content of ∼0.2%. For a higher density of vacancies, the elastic modulus decreases with defect inclusions. The initial increase in Young’s modulus is explained in terms of a dependence of the elastic coefficients on the momentum of flexural modes predicted for two-dimensional membranes 4 , 5 . In contrast, the fracture strength decreases with defect density according to standard fracture continuum models. These quantitative structure–property relationships, measured in atmospheric conditions, are of fundamental and technological relevance and provide guidance for applications in which graphene mechanics represents a disruptive improvement.