Heterostructures of 2D materials are expected to become building blocks of next generation nanoelectronic devices. Therefore, the detailed understanding of their interfaces is of particular importance. In order to gain information on the properties of the graphene - MoS2 system, we have investigated MoS2 sheets grown by chemical vapour deposition (CVD) on highly ordered pyrolytic graphite (HOPG) as a model system with atomically clean interface. The results are compared with results reported recently for MoS2 grown on epitaxial graphene on SiC. Our STM study revealed that the crystallographic orientation of MoS2 sheets is determined by the orientation of the underlying graphite lattice. This epitaxial orientation preference is so strong that the MoS2 flakes could be moved on HOPG with the STM tip over large distances without rotation. The electronic properties of the MoS2 flakes have been investigated using tunneling spectroscopy. A significant modification of the electronic structure has been revealed at flake edges and grain boundaries. These features are expected to have an important influence on the performance of nanoelectronic devices. We have also demonstrated the ability of the STM to define MoS2 nanoribbons down to 12 nm width, which can be used as building blocks for future nanoelectronic devices.
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