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

Large-area two-dimensional MoSe₂/WSe₂ and WSe₂/MoSe₂ heterostructures have been successfully fabricated using molecular-beam epitaxy. Highly oriented heterostructures are composed of alternately stacked epitaxial MoSe₂ and WSe₂ monolayers (MLs) on Se-treated GaAs(111)B substrates with nearly stoichiometric compositions. The MoSe₂ and WSe₂ 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 MoSe₂ and WSe₂ MLs.