Suppression of step bunching in graphene growth on 4° off-axis SiC (0001) by a two-step growth technique

Step bunching during graphene growth on 4° off-axis SiC (0001) was effectively suppressed using a two-step growth technique. In the first step, a graphene buffer layer was obtained under vacuum. In the following step, additional graphene layers were grown under an argon atmosphere at atmospheric pressure, with good control over the number of layers. The first-step layer played a key role in suppressing step bunching during the second step, resulting in a one-order-of-magnitude reduction in surface roughness compared to a conventional growth method exclusively using an argon atmosphere. The effect of the off-angle on step bunching was also investigated by analyzing the differences between on-axis and 4° off-axis substrates. Our findings suggest that atomic diffusion is restricted by the presence of the graphene buffer layer.