Surface Diffusion in SnTe‐PbTe Monolayer Lateral Heterostructures

ABSTRACT The construction of complex functional heterostructures from low‐dimensional materials requires creating atomically sharp vertical and lateral interfaces. While vertical heterostructures of 2D materials can be readily formed through stacking, the growth of lateral heterostructures faces a larger challenge and is relatively less understood. Particularly, suppressing atomic or molecular interdiffusion at lateral heterointerfaces is critical for obtaining atomically sharp 2D lateral heterostructures. Here, using in situ scanning tunneling microscopy, we observe a surface diffusion mechanism that becomes dominant at the molecular beam epitaxially grown 1D interfaces of lateral heterostructures between SnTe and PbTe monolayers, which are 2D ferroelectric and paraelectric semiconductors, respectively. This mechanism, which does not exist in the vertical heterostructures with 2D interfaces, is responsible for the asymmetric interdiffusion at the two different types of interfaces—those with PbTe grown outside of SnTe, and those with SnTe grown outside of PbTe. By optimizing the relative parameters including substrate temperature, molecular fluxes, and the thickness of the graphene substrate, we have realized nearly atomically sharp lateral heterointerfaces with suppressed interdiffusion. This study paves the way to creating clean and sharp SnTe‐PbTe interfaces for valleytronic and quantum information devices that require ultra‐narrow lateral heterostructures.