Elimination of Grain Boundaries in Graphene Growth on a Cu-Ni Alloyed Substrate by Chemical Vapor Deposition

The controlled growth of large-area single-crystalline graphene via epitaxial methods such as chemical vapor deposition (CVD) is essential in the eventual widespread realization of graphene-based devices. In this endeavor, one startling obstacle is the emergence of abundant grain boundaries in a growing graphene layer. Here, we carry out comparative studies of single-layer graphene films grown on optimized Cu(111) and Cu-Ni(111) alloyed substrates using various experimental probes and first-principles calculations. We demonstrate, convincingly, that the use of the Ni substitutionally alloyed Cu substrate results in drastic elimination of grain boundaries in graphene films compared to those grown on pure Cu. The underlying mechanism of the highly preferred single-crystalline growth is the elimination of the orientational disorder of multiple initial nucleation islands on the Cu-Ni(111) surface, as demonstrated theoretically and confirmed experimentally. The present study not only unveils the atomistic growth mechanism of single-crystalline monolayered graphene on Cu-Ni alloys with a fast growth rate and mass productivity but also sheds light on the controlled CVD growth of large-area twist-angle bilayer graphene, multilayered graphene, and other 2D vdW materials in general.