Structural and optical characterization of nanometer sized MoS2/graphene heterostructures for potential use in optoelectronic devices

Two-dimensional (2D) transition metal dichalcogenide (TMD) semiconductors, with MoS2 as the most widely researched one, have large potential for development of novel devices. This calls for scalable and controllable fabrication of TMD monolayers and their heterostructures with high-quality interfaces, controllable stack orientation and pristine properties. Molecular Beam Epitaxy (MBE) allows the growth of 2D van der Waals materials and offers unparalleled control of cleanliness and growth parameters. However, these advantages are limited by eligible growth substrates, which are often incompatible with the desired application. Here we show the growth of a heterostructure based on nanometer sized MoS2 islands on a macroscopic graphene sheet on Ir (1 1 1) and the subsequent transfer of the heterostructure to a Si wafer. The heterostructure is delaminated from the substrate by a two-step electrochemical process involving a sacrificial PMMA layer to ensure efficient transfer. Detailed scanning probe and spectroscopic characterization at different stages of the process confirm the high sample quality, which is maintained throughout the procedure. This method remedies the substrate constraints imposed by MBE and allows to harness its quality and tunability for applications in photonics, electronics and quantum technology.