Graphene–Ni(111) Synergy Influencing Crystalline Orientation, Grain Morphology and Magnetic Properties of Poly-Ni

Abstract

Among many metal catalyst surfaces, graphene growth on Ni(111) is highly facile owing to the least lattice mismatch between the two. Although the influence of crystalline orientation of Ni on the quality and properties of graphene is known, the effect of this growth on the catalyst surface is not well studied. In the present study, we have investigated this aspect by growing twisted multilayer graphene on polycrystalline Ni foil by a modified CVD process and examined the Ni surface carefully by employing a host of experimental techniques. X-ray diffraction measurements clearly indicate enhancement in the (111) orientation following graphene growth which is corroborated by the electron backscatter diffraction maps. There is an overall increase in the grain size as well, as evidenced by electron microscopy. Further, the ferromagnetic Curie temperature of Ni exhibits a downward shift of up to ∼80 K as also does saturation magnetization, by ∼0.06 μB. The changes in properties are accompanied by unusual morphological events on the Ni surface which include sharpening and interlocking of grain boundaries and cleavage formation. The above observations clearly point to a synergetic effect that manifests at the graphene–Ni(111) interface, the twisted layers only amplifying the effect.