Epitaxial (111) films of Cu, Ni, and CuxNiy on α-Al2O3 (0001) for graphene growth by chemical vapor deposition

Films of (111)-textured Cu, Ni, and CuxNiy were evaluated as substrates for chemical vapor deposition of graphene. A metal thickness of 400 nm to 700 nm was sputtered onto a substrate of alpha-Al2O3(0001) at temperatures of 250 degrees C to 650 degrees C. The films were then annealed at 1000 degrees C in a tube furnace. X-ray and electron backscatter diffraction measurements showed all films have (111) texture but have grains with in-plane orientations differing by 60 degrees. The in-plane epitaxial relationship for all films was inverted right perpendicular110inverted left perpendicular(metal)parallel to inverted right perpendicular10 (1) over bar 0inverted left perpendicular(Al2O3). Reactive sputtering of Al in O-2 before metal deposition resulted in a single in-plane orientation over 97% of the Ni film but had no significant effect on the Cu grain structure. Transmission electron microscopy showed a clean Ni/Al2O3 interface, confirmed the epitaxial relationship, and showed that formation of the 60 degrees twin grains was associated with features on the Al2O3 surface. Increasing total pressure and Cu vapor pressure during annealing decreased the roughness of Cu and CuxNiy films. Graphene grown on the Ni(111) films was more uniform than that grown on polycrystalline Ni/SiO2 films, but still showed thickness variations on a much smaller length scale than the distance between grains. [http://dx.doi.org/10.1063/1.4754013]