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Edge magnetism in zigzag nanoribbons of monolayer MoS 2 has been investigated with both density functional theory and a tight-binding plus Hubbard (TB+U) Hamiltonian. Both methods revealed that one band crossing the Fermi level is more strongly influenced by spin polarization than any other bands. This band originates from states localized on the sulfur edge of the nanoribbon. Its dispersion closely resembles that of the energy branch obtained in a linear chain of atoms with first-neighbor interaction. By exploiting this resemblance, a toy model has been designed to study the energetics of different spin configurations of the nanoribbon edge. [ABSTRACT FROM AUTHOR]

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 – MoS 2 system, we have investigated MoS 2 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 MoS 2 grown on epitaxial graphene on SiC. Our STM study revealed that the crystallographic orientation of MoS 2 sheets is determined by the orientation of the underlying graphite lattice. This epitaxial orientation preference is so strong that the MoS 2 flakes could be moved on HOPG with the STM tip over large distances without rotation. The electronic properties of the MoS 2 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 MoS 2 nanoribbons down to 12 nm width, which can be used as building blocks for future nanoelectronic devices. [ABSTRACT FROM AUTHOR]

The possibility that non-magnetic materials such as carbon could exhibit a novel type of s-p electron magnetism has attracted much attention over the years, not least because such magnetic order is predicted to be stable at high temperatures. It has been demonstrated that atomic-scale structural defects of graphene can host unpaired spins, but it remains unclear under what conditions long-range magnetic order can emerge from such defect-bound magnetic moments. Here we propose that, in contrast to random defect distributions, atomic-scale engineering of graphene edges with specific crystallographic orientation-comprising edge atoms from only one sub-lattice of the bipartite graphene lattice-can give rise to a robust magnetic order. We use a nanofabrication technique based on scanning tunnelling microscopy to define graphene nanoribbons with nanometre precision and well-defined crystallographic edge orientations. Although so-called 'armchair' ribbons display quantum confinement gaps, ribbons with the 'zigzag' edge structure that are narrower than 7 nanometres exhibit an electronic bandgap of about 0.2-0.3 electronvolts, which can be identified as a signature of interaction-induced spin ordering along their edges. Moreover, upon increasing the ribbon width, a semiconductor-to-metal transition is revealed, indicating the switching of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferromagnetic configuration. We found that the magnetic order on graphene edges of controlled zigzag orientation can be stable even at room temperature, raising hopes of graphene-based spintronic devices operating under ambient conditions. [ABSTRACT FROM AUTHOR]