Large-Scale Synthesis of Graphene Films by Joule-Heating-Induced Chemical Vapor Deposition

We report large-area synthesis of few-layer graphene films by chemical vapor deposition (CVD) in a cold-wall reactor. The key feature of this method is that the catalytic metal layers on the SiO₂/Si substrates are self-heated to high growth temperature (900°C to 1000°C) by high-current Joule heating. Synthesis of high-quality graphene films, whose structural and electrical characteristics are comparable to those grown by hot-wall CVD systems, was confirmed by transmission electron microscopy images, Raman spectra, and current–voltage analysis. Optical transmittance spectra of the graphene films allowed us to estimate the number of graphene layers, which revealed that high-temperature exposure of Ni thin layers to a carbon precursor (CH₄) was critical in determining the number of graphene layers. In particular, exposure to CH₄ for 20 s produces very thin graphene films with an optical transmittance of 93%, corresponding to an average layer number of three and a sheet resistance of ~600 Ω/square.