Direct Measurement of Adhesion Energy of Monolayer Graphene As-Grown on Copper and Its Application to Renewable Transfer Process

Direct measurement of the adhesion energy of monolayer graphene as-grown on metal substrates is important to better understand its bonding mechanism and control the mechanical release of the graphene from the substrates, but it has not been reported yet. We report the adhesion energy of large-area monolayer graphene synthesized on copper measured by double cantilever beam fracture mechanics testing. The adhesion energy of 0.72 ± 0.07 J m^–2 was found. Knowing the directly measured value, we further demonstrate the etching-free renewable transfer process of monolayer graphene that utilizes the repetition of the mechanical delamination followed by the regrowth of monolayer graphene on a copper substrate

Healing Graphene Defects Using Selective Electrochemical Deposition: Toward Flexible and Stretchable Devices

Graphene produced by chemical-vapor-deposition inevitably has defects such as grain boundaries, pinholes, wrinkles, and cracks, which are the most significant obstacles for the realization of superior properties of pristine graphene. Despite efforts to reduce these defects during synthesis, significant damages are further induced during integration and operation of flexible and stretchable applications. Therefore, defect healing is required in order to recover the ideal properties of graphene. Here, the electrical and mechanical properties of graphene are healed on the basis of selective electrochemical deposition on graphene defects. By exploiting the high current density on the defects during the electrodeposition, metal ions such as silver and gold can be selectively reduced. The process is universally applicable to conductive and insulating substrates because graphene can serve as a conducting channel of electrons. The physically filled metal on the defects improves the electrical conductivity and mechanical stretchability by means of reducing contact resistance and crack density. The healing of graphene defects is enabled by the solution-based room temperature electrodeposition process, which broadens the use of graphene as an engineering material