Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils

The highest quality graphene samples, single-atom-thick layers of carbon, are suspended flakes exfoliated from graphite, but these samples are very small in size (square micrometers). For many electronics applications, larger areas are needed. Li et al. (p. 1312, published online 7 May) show that graphene grows in a self-limiting way on copper films as large-area sheets (one square centimeter) from methane through a chemical vapor deposition process. The films, which are mainly one layer in thickness, can be transferred to other substrates and have electron mobilities as high as 4300 square centimeters per volt second.

Graphene has been attracting great interest because of its distinctive band structure and physical properties. Today, graphene is limited to small sizes because it is produced mostly by exfoliating graphite. We grew large-area graphene films of the order of centimeters on copper substrates by chemical vapor deposition using methane. The films are predominantly single-layer graphene, with a small percentage (less than 5%) of the area having few layers, and are continuous across copper surface steps and grain boundaries. The low solubility of carbon in copper appears to help make this growth process self-limiting. We also developed graphene film transfer processes to arbitrary substrates, and dual-gated field-effect transistors fabricated on silicon/silicon dioxide substrates showed electron mobilities as high as 4050 square centimeters per volt per second at room temperature.