Effect of initially formed graphene grain size on the crystallinity of graphene from mobile hot-wire-assisted chemical vapor deposition system

Abstract

Chemical vapor deposition method among the graphene synthesis methods has an advantage of producing high quality graphene in a large area, but it has a limitation that it can not show the excellent characteristics of the theoretically known graphenes because of the polycrystalline structure. In order to synthesize single crystal graphene, we have developed a mobile hot wire chemical vapor deposition system that adds heating source for local and continuous heat treatment. In this system, randomly oriented grains are initially formed and then when local and continuous heat treatment is performed on the grains they are rotated in the same direction as the surrounding grains. However, the grains that were tilted by about 30 degrees from the surrounding crystals remain because they are energetically metastable. In this study, the size of the initially formed grains was reduced in order to weaken the interaction of the graphene-metal substrate and facilitate rotation of the high angle tilted domains . To control the domain size, nucleation density is increased by adding nickel to the copper and it was confirmed the grain size is decreased. We identified that the remained high angle tilted grains in the the finally formed graphene with optimized growth condition were significantly reduced in graphene grown on Cu Ni alloy compared to that grown on pure Cu via transmission electron microscope.