Two-Dimensional WSe₂/MoSe₂ Heterostructures Grown by Molecular-Beam Epitaxy

Large-area two-dimensional MoSe 2 /WSe 2 and WSe 2 /MoSe 2 heterostructures have been successfully fabricated using molecular-beam epitaxy. Highly oriented heterostructures are composed of alternately stacked epitaxial MoSe 2 and WSe 2 monolayers (MLs) on Se-treated GaAs(111)B substrates with nearly stoichiometric compositions. The MoSe 2 and WSe 2 MLs are weakly bonded together and show either the stable C7 or the T stacking configuration, irrespective of the stacking order. We further demonstrate that the four-layered heterostructures are realized by the successive growth of MoSe 2 and WSe 2 MLs.