Lateral and vertical heterostructures in two-dimensional transition-metal dichalcogenides [Invited]

Heterostructures (HSs) of two-dimensional (2D) transition-metal dichalcogenides (TMDs) offer a plethora of opportunities in materials science, condensed-matter physics, and device engineering. The out-of-plane van der Waals interaction of 2D TMDs with surrounding environments enables the synthesis of HSs on virtually any substrate. This unmatched quality gives TMD HSs a superior edge in applications such as flexible optoelectronics in which III-V HSs are still struggling with lattice-mismatch issues. 2D TMDs can be vertically stacked or lateral stitched to form vertical (i.e., out-of-plane) or lateral (i.e., in-plane) heterojunctions, respectively. Motivated by the critical impact of synthesis methods on the progress of this field, in this article, we have reviewed the state-of-the-art synthesis techniques employed for the creation of lateral and vertical junctions between heterogenous TMD films. At the end of this article, we have also briefly reviewed the spectroscopic characterization of TMD heterojunctions. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement