▎ 摘　　要

The reusability of Ir(111)/alpha-Al2O3(0001) substrates for graphene CVD in multiple cycles was studied. Better reusability was obtained by using Ir layers prepared at a high growth temperature, 1150 degrees C, which had a stable surface morphology in the multiple CVD cycles. Multilayer graphene islands were observed in the graphene films grown in the multiple CVD cycles, which was attributed to the carbon atoms dissolved during the previous CVD cycle. A method combining annealing, quenching, and oxygen plasma etching was proposed to remove the residual carbon atoms in the Ir layers. We succeeded in growing uniform monolayer graphene films in the multiple CVD cycles using the same Ir(111)/alpha-Al2O3(0001) substrate. (c) 2020 The Japan Society of Applied Physics