Interaction with the substrate strongly affects the electronic/chemical properties of supported graphene. So far, graphene deposited by chemical vapor deposition (CVD) on catalytic single crystal transition metal surfaces -mostly 3-fold close-packed -has mainly been studied. Herein, we investigated CVD graphene on a polycrystalline nickel (Ni) substrate, focusing in particular on (100) micrograins and comparing the observed behavior with that on single crystal Ni(100) substrate. The symmetry-mismatch leads to moiré superstructures with stripe-like or rhombic-network morphology, which were characterized by atomically-resolved scanning tunneling microscopy (STM). Density functional theory (DFT) simulations shed light on spatial corrugation and interfacial interactions: depending on the misorientation angle, graphene is either alternately physi-and chemisorbed or uniformly chemisorbed, the interaction being modulated by the (sub)nanometer-sized moiré superstructures. Ni(100) micrograins appear to be a promising substrate to finely tailor the electronic properties of graphene at the nanoscale, with relevant perspective applications in electronics and catalysis. of the graphene lattice, which leads to alternate strongly-and weakly-interacting regions across the moiré supercells [13][14][15][16][17][18]. In contrast, the weak coupling between graphene and other transition metals (such as copper (Cu), iridium (Ir) and platinum) results in large interfacial spacing out of the range of chemisorption, smaller spatial corrugation of moirés with respect to strongly-coupled systems, and limited rotational alignment between graphene and the substrate [19][20][21][22][23]. From an electronic point of view, the band structures for chemisorbed graphene (such as that on Ni(111) or Ru(0001)) are fragmented or disrupted due to the hybridization of the graphene π state and the metal d orbital, while physisorbed graphene typically shows Dirac cones similar to its pristine form [24][25][26]. Therefore, the magnitude of energy gap opening, interface charge polycrystalline Ni foils are also explored, thereby bridging the material gap from single crystal to realistic, non-ideal surfaces for STM measurements. Indeed, the (100) facet is one of the most common orientations present in polycrystalline Ni foils or thin films, as reported in literature [29,37] and further corroborated in this work. In addition, nickel is among the class of most-utilized metallic catalysts for CVD growth of graphene [5][6]38]. This work is therefore of potential interest for the scalable production and applications of graphene. Our results indicate that graphene structures observed on both single-and poly-crystalline substrates are highly nanometer scale. Generally, graphene moiré originates from lattice mismatch and/or angular misorientation in two isosymmetric overlapping periodic lattices; herein the situation is further complicated by the symmetry mismatch of the two interface lattices. In figures 2(a-c), from left to right, we show three STM images with incr...
