Roles of CuO and Cu2O in graphene growth on a copper substrate

In chemical vapor deposition, oxygen plays an important role during graphene growth, especially in the case of copper substrates. However, currently, there is inconsistent information on the role of oxygen in graphene growth. In this study, the mechanism of pre-oxidation on copper substrate to reduce the nucleation density was explored, and the effects of the oxidation products (CuO and Cu2O) introduced on copper substrates under different oxygen partial pressures were discussed. CuO and Cu2O were found to be beneficial in promoting graphene nucleation and growth. The Cu2O surface exhibited greater C absorption activity than the Cu2O/Cu (111) step, which was completely opposite to that of CuO on the Cu(111) substrate. A uniform Cu2O layer with a thickness of < 10 nm was prepared to promote graphene growth on the Cu(111) substrate; thereby, a monolayer single-crystalline graphene was achieved. This work provides new data for the preparation of high-quality monolayer graphene on copper substrate.