Post-Synthesis Modifications of Two-Dimensional MoSe or MoTe by Incorporation of Excess Metal Atoms into the Crystal Structure.

Phase engineering has extensively been used to achieve metallization of two-dimensional (2D) semiconducting materials, as it should boost their catalytic properties or improve electrical contacts. In contrast, here we demonstrate compositional phase change by incorporation of excess metals into the crystal structure. We demonstrate post-synthesis restructuring of the semiconducting MoTe or MoSe host material by unexpected easy incorporation of excess Mo into their crystal planes, which causes local metallization.

Strong room-temperature ferromagnetism in VSe monolayers on van der Waals substrates.

Reduced dimensionality and interlayer coupling in van der Waals materials gives rise to fundamentally different electronic , optical and many-body quantum properties in monolayers compared with the bulk. This layer-dependence permits the discovery of novel material properties in the monolayer regime. Ferromagnetic order in two-dimensional materials is a coveted property that would allow fundamental studies of spin behaviour in low dimensions and enable new spintronics applications.

Metallic Twin Grain Boundaries Embedded in MoSe Monolayers Grown by Molecular Beam Epitaxy.

Twin grain boundaries in MoSe are metallic and undergo a metal to insulator Peierls transition at low temperature. Growth of MoSe by molecular beam epitaxy results in the spontaneous formation of a high density of these twin grain boundaries, likely as a mechanism to incorporate Se deficiency in the film. Using scanning tunneling microscopy, we study the grain boundary network that is formed in homoepitaxially grown MoSe and for MoSe grown heteroepitaxially on MoS and HOPG substrates.

Angle resolved photoemission spectroscopy reveals spin charge separation in metallic MoSe grain boundary.

Material line defects are one-dimensional structures but the search and proof of electron behaviour consistent with the reduced dimension of such defects has been so far unsuccessful. Here we show using angle resolved photoemission spectroscopy that twin-grain boundaries in the layered semiconductor MoSe exhibit parabolic metallic bands. The one-dimensional nature is evident from a charge density wave transition, whose periodicity is given by k/π, consistent with scanning tunnelling microscopy and angle resolved photoemission measurements.

Direct observation of interlayer hybridization and Dirac relativistic carriers in graphene/MoS₂ van der Waals heterostructures.

Artificial heterostructures assembled from van der Waals materials promise to combine materials without the traditional restrictions in heterostructure-growth such as lattice matching conditions and atom interdiffusion. Simple stacking of van der Waals materials with diverse properties would thus enable the fabrication of novel materials or device structures with atomically precise interfaces. Because covalent bonding in these layered materials is limited to molecular planes and the interaction between planes are very weak, only small changes in the electronic structure are expected by stacking these materials on top of each other.

Seeding atomic layer deposition of alumina on graphene with yttria.

Integrating graphene into nanoelectronic device structure requires interfacing graphene with high-κ dielectric materials. However, the dewetting and thermal instability of dielectric layers on top of graphene makes fabricating a pinhole-free, uniform, and conformal graphene/dielectric interface challenging. Here, we demonstrate that an ultrathin layer of high-κ dielectric material Y2O3 acts as an effective seeding layer for atomic layer deposition of Al2O3 on graphene.

Interface properties of CVD grown graphene transferred onto MoS2(0001).

Heterostructures of dissimilar 2D materials are potential building blocks for novel materials and may enable the formation of new (photo)electronic device architectures. Previous work mainly focused on supporting graphene on insulating wide-band gap materials, such as hex-BN and mica. Here we investigate the interface between zero-band gap semiconductor graphene and band-gap semiconductor MoS2 as a potential building block for entirely 2D-material based semiconducting devices.