Evaluation and healing of graphene defects

Abstract

Graphene has successfully shown its superior properties beyond existing physical limitations. The development of chemical vapor deposition (CVD) on catalyst metals enabled the synthesis of large-area and high-quality graphene. To preserve the ideal properties in graphene and ensure the reliability in applications, the defects should be minimized. However, during the synthesis, integration, and operation of graphene devices, numerous defects are inevitably formed

therefore, evaluation and healing of the defects are required. In this dissertation, I have focused on the evaluation and healing of graphene defects. Based on the oxidation of catalyst metal, graphene defects were visualized on as-grown substrates. The penetration and lateral diffusion characteristics were investigated for a diffusion barrier application. However, the oxidation method cannot be used on a transferred substrate, and induces significant damage on graphene. Therefore, the non-destructive defect visualization method was further developed based on the electrochemical reduction of metal. Because of the local charge concentration, the defects were selectively decorated with metal, and furthermore it was demonstrated on various substrates such as polymers, ceramics, and metals. Moreover, the graphene defects were quantitative evaluated by the electromagnetic induction. The induced voltage on graphene represents the degree of defect, which was verified by experiments and theoretical calculations. It is significant that the induced voltage is decoupled from the conductivity change of graphene. The electrodeposition of metal also enabled the healing of graphene defects. The electrical and mechanical properties of defective graphene were effectively healed by controlling the electrodeposition. Furthermore, the external damages of strain and surface scratch were induced on graphene, and the electrical property was recovered after the healing process. The roughness prediction model was proposed for the healed graphene, and limitations of the electrodeposition process was discussed.