One-dimensional metallic grain boundary in transition metal dichalcogenides

Abstract

In contrast to their more often detrimental role, large-angle (60°) grain boundaries (GBs) provide opportunities to tailor the properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs), bringing new functionalities and exciting opportunities to form intrinsic electronic heterostructures within monolayer TMDCs. In domains facing the GBs, polarization vectors along armchair direction are inversed and thus polar discontinuity arises at the GBs, as a consequence of nonzero bulk polarization of TMDCs. In order to screen the polarization charge, which gives rise to an electric field, depending on the bonding nature at GBs free electrons or holes are driven to accumulate on the GBs leading to the dispersive boundary states of metallicity. In particularly, 60° GBs in 2D TMDCs can behave as one-dimensional (1D) metallic quantum wires, serving as 1D channels for free carriers or excitons.