LAUSR

Group 14 elemental post‐graphene materials receive much attention because of their outstanding properties, typically, as robust 2D topological insulators. Their heterostructures are a main target in view of disruptive applications. Here, the realization of striking in‐plane lateral heterostructures between germanene and stanene are shown, which are sustainable 2D Ge‐ and Snbased graphene analogs, but with a strong intrinsic spin–orbit coupling. A unique combination of atomic segregation epitaxy (ASE) and molecular beam epitaxy (MBE) for the in situ continuous fabrication of nearly atomically precise lateral multijunction heterostructures, respectively, consisting of atom‐thin germanene and stanene on a Ag(111) thin film is used. Scanning tunneling microscopy (STM) observations at atomic scale and low‐energy electron diffraction testify that germanene and stanene sheets without intermixing are prepared simultaneously on the same terraces at wide scale: tin and germanium atoms neither exchange their sites nor adsorb on the germanene and stanene sheets. The atomic structure of the boundary between germanene and stanene is derived from STM images, while scanning tunneling spectroscopy reveals key electronic features at the heterojunction. This innovative synergetic approach of ASE and MBE growths offers great flexibility for the realization of unprecedented lateral 2D heterostructures.