Abstract
Single-crystal graphene has attracted much attention due to its excellent electrical properties in recent years, and many growth methods have been proposed, including the copper pockets method. In the copper pockets method, a piece of copper foil is folded into a pocket and put into a chemical vapor deposition (CVD) system for the growth of graphene. The dynamic balance of evaporation and deposition of copper on the inner surfaces of the copper pockets avoids high surface roughness caused by the evaporation of copper in open space, such as the outer surfaces of copper pockets. Much lower partial pressure of methane in the copper pockets and lower surface roughness reduce the nucleation density of graphene and increase the size of single-crystal graphene. It is found that the growth pressure is closely related to the size of single-crystal graphene prepared by the copper pockets method; the higher the growth pressure, the larger the size of single-crystal graphene. It is also found that the growth pressure has an effect on the inner surface roughness of the copper pockets, but the effect is not significant. The main factor affecting the size of the single-crystal graphene is the change in the volume of the copper pockets caused by the change in the growth pressure, and the volume of the copper pockets determines the content of methane in the copper pockets. According to the above law, the size of single-crystal graphene prepared by the copper pockets method can be enlarged by increasing the growth pressure. The size of single-crystal graphene can be enlarged in a wide range as the growth pressure can be increased in a wide range. In our experiments, when the growth pressure reached 450 Pa, single-crystal graphene with a diameter of 450 was prepared.
Highlights
The thinnest carbon material with atoms arranged in a two-dimensional hexagonal lattice, was first isolated by mechanical exfoliation from highly oriented pyrolytic graphite (HOPG) and has exceptional chemical stability, superior mechanical stability, very high thermal conductivities and electronic conductivities [1,2,3]
Various methods to synthesize graphene have been developed to address these challenges, among which chemical vapor deposition (CVD) has emerged as the most promising technique owing to its capability to provide high-quality, large-area production, controllability of the number of layers, and good repeatability [10]
The copper pockets were placed flat in the quartz boat, which was located in the center of the quartz tube of CVD system
Summary
The thinnest carbon material with atoms arranged in a two-dimensional hexagonal lattice, was first isolated by mechanical exfoliation from highly oriented pyrolytic graphite (HOPG) and has exceptional chemical stability, superior mechanical stability, very high thermal conductivities and electronic conductivities [1,2,3]. The best-quality graphene has been obtained by mechanically exfoliating highly oriented pyrolytic graphite [1]. This method is limited by poor scalability considering the limited size of graphene flakes and the difficulty in carefully controlling the number of layers. Since the day the CVD method appeared, there are still lots of challenges, such as controlling the number of graphene layers, minimizing wrinkling, and increasing the size of single crystals [13]
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