Controlled Growth of Single‐Crystal Graphene Wafers on Twin‐Boundary‐Free Cu(111) Substrates

Abstract Single‐crystal graphene (SCG) wafers are needed to enable mass‐electronics and optoelectronics owing to their excellent properties and compatibility with silicon‐based technology. Controlled synthesis of high‐quality SCG wafers can be done exploiting single‐crystal Cu(111) substrates as epitaxial growth substrates recently. However, current Cu(111) films prepared by magnetron sputtering on single‐crystal sapphire wafers still suffer from in‐plane twin boundaries, which degrade the SCG chemical vapor deposition. Here, it is shown how to eliminate twin boundaries on Cu and achieve 4 in. Cu(111) wafers with ≈95% crystallinity. The introduction of a temperature gradient on Cu films with designed texture during annealing drives abnormal grain growth across the whole Cu wafer. In‐plane twin boundaries are eliminated via migration of out‐of‐plane grain boundaries. SCG wafers grown on the resulting single‐crystal Cu(111) substrates exhibit improved crystallinity with >97% aligned graphene domains. As‐synthesized SCG wafers exhibit an average carrier mobility up to 7284 cm 2 V −1 s −1 at room temperature from 103 devices and a uniform sheet resistance with only 5% deviation in 4 in. region.