In situ scanning electron microscopy (SEM) was used for observing the nucleation of graphene by segregation of bulk-dissolved carbon on a flat polycrystalline nickel surface. Preferential nucleation sites were determined on large (111) grains. In combination with ex situ atomic force microscopy measurements at the same area as with SEM, the nucleation sites were found to have step-bunched structures. Possible nucleation mechanisms are discussed based on the difference in the carbon concentration and critical nucleus size between the (111) terrace and step bunches.
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