Two-dimensional Xene Heterostructures by Epitaxy

The synthesis of new Xenes and their potential applications prototypes have achieved significant milestones so far. However, to date the realization of Xene heterostructures in analogy with the well-known van der Waals heterostructures remains an unresolved issue. Here, we introduce a Xene heterostructure concept based on the epitaxial combination of silicene and stanene on Ag(111), and demonstrate how one Xene layer enables another Xene layer of different nature to grow on top. We synthesized single-phase (4 x 4) silicene using stanene as a template, and managed to grow stanene on top of silicene on the other way around. In both heterostructures <em>in situ</em> and <em>ex situ</em> probes confirm layer-by-layer growth without intercalations and intermixing. Modelling via Density Functional Theory (DFT) shows that the atomic layers in the heterostructures are strongly interacting and hexagonal symmetry conservation in each individual layer is sequence-selective. Our results provide a substantial step towards currently missing Xene heterostructures and open the door to a new frontier of atomic-scale materials engineering.