Effects of three parameters on graphene synthesis by chemical vapor deposition

A high quality graphene film on a copper foil was successfully grown by a CVD process using ethanol as a carbon source. The effect of growth temperatures (650-850°C), reaction times (5-50 min) and post-CVD cooling process rates (slow-cooling, fast-cooling and fast-cooling under ethanol exposure) on the formation of graphenes was investigated by Raman spectroscopy and scanning electron microscopy (SEM). The graphene film deposited under the optimal conditions showed features of a high quality such as a high I_2D/I_G ratio of ~8, a low ID/IG ratio of 0.28 and a narrow full width half maximum (FWHM) of Lorentzian-shaped 2D peak of ~35 cm^-1. It was found that the quality of graphene film could be enhanced by optimizing the growth temperature and time, while the number of graphene layer was less sensitive to the cooling rate. However, the fast cooling process under ethanol exposure was found to be a key process for obtaining graphenes with a large domain size. These findings may help to fabricate high-quality graphenes on a copper foil for electronic applications.