We investigated the growth of graphene by molecular beam epitaxy (MBE) using cracked ethylene as a growth source gas under various growth conditions. The analyses of the C 1 s core-level photoelectron spectra and the D-, G-, and 2D-band peaks in Raman spectra revealed that graphene was successfully grown by MBE when cracked ethylene was used as a source gas. Analyses of surface morphology by atomic force microscopy and the substrate temperature dependence of the grown graphene thicknesses indicated that the graphene growth process is essentially the same as that for ethanol. Furthermore, when graphene was grown under a high vacuum, the flow-rate dependence of the deposition rate of graphitic materials demonstrated the expected trend that the deposition rate increased with increasing flow rate. In addition, we found that use of the ethylene improves the domain size of the MBE graphene and that the high-vacuum growth further enhances it, suggesting that the migration enhancement of the growth materials is the key to improving the quality of the graphene in MBE growth. (c) 2013 Elsevier B.V. All rights reserved.