Synthesis of large-area graphene films on rolled-up Cu foils by a "breathing" method

Chemical vapor deposition (CVD) is considered to be the most promising method for the synthesis of large-area high-quality graphene films. However, with an increase in reactor size, manufacturing difficulty and significant increases in CVD reactor costs will occur. These effects result in considerable limitations on the size and throughput of graphene films. We report a "breathing" CVD method to effectively utilize the reactor space for producing large-area graphene films with a small reactor. A rectangular Cu foil substrate is rolled into a spiral to increase the substrate loading density. Graphite mat strips are placed between the Cu layers at the two ends of the spiral to avoid Cu layer adhesion at high temperature while leaving enough space inside the Cu spiral for gas exchange. Reactant gases are introduced in a way similar to breathing by repeatedly increasing and decreasing the pressure inside the reactor as well as the Cu spiral, which assists gas exchange. In addition, in order to avoid the collapse of the middle Cu layers due to high temperature softening and gravity, the Cu spiral is placed vertically. With this method, both the size and throughput of graphene films can be an order of magnitude larger than conventional methods, as demonstrated by the synthesis of the large-area high-quality graphene films of 1.1 m x 0.25 m with a 2-in. diameter quartz tube CVD reactor. The transverse length (1.1 m) of the graphene film is 25 times the inner diameter (0.044 m) of the reactor tube. This method can also be used for the synthesis of other large-area 2D films and the production of large-area metal single crystal foils.