Templated growth and intercalation pathways of nickel nanoclusters on graphene/Ir(111)

The growth and intercalation of nickel (Ni) nanoclusters on the moiré superlattice of graphene(Gr)/Ir(111) were investigated by scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions. At room temperature (RT), Ni deposition led to the formation of flat, triangular islands, with nucleation preferentially occurring at fcc regions of the moiré superlattice. These islands evolved into three-dimensional triangular nanoclusters that were aligned with the substrate's close-packed directions, reflecting the templating effect of the graphene moiré. Upon annealing to 900 K, Ni atoms intercalated beneath the graphene layer, yielding two distinct moiré contrasts signifying different local intercalation configurations. These findings demonstrate that Ni nanostructures confined by the moiré template provide a well-defined platform for exploring size- and shape-dependent properties relevant to catalytic and magnetic applications.