  Ultrathin lateral heterostructures of monolayer MoS2 and WS2 have
successfully been realized with the metal-organic chemical vapor deposition
method. Atomic-resolution HAADF-STEM observations have revealed that the
junction widths of lateral heterostructures range from several nanometers to
single-atom thickness, the thinnest heterojunction in theory. The interfaces
are atomically flat with minimal mixing between MoS2 and WS2, originating from
rapid and abrupt switching of the source supply. Due to one-dimensional
interfaces and broken rotational symmetry, the resulting ultrathin lateral
heterostructures, 1~2 mixed-dimensional structures, can show emergent
optical/electronic properties. The MOCVD growth developed in this work allows
us to access various ultrathin lateral heterostructures, leading to future
exploration of their emergent properties absent in each component alone.
