Honeycomb germanene flakes on Ag nano-islands

As germanene cannot be exfoliated from a bulk material, and as Ge-based surface alloys are more stable than pure Ge monolayers on metal surfaces, the synthesis of germanene flakes is challenging. Here we report on the synthesis of germanene nanoflakes on Ag monolayer islands on Ag(111). The maximum achievable size is of the order of 30 nm, and germanene growth occurs thanks to heavily oversaturated chemical potential for the Ge atoms confined on top of the Ag islands during growth. Nucleation of 3D clusters hinders the formation of larger germanene flakes.