Controlling Morphology and Excitonic Disorder in Monolayer WSe2 Grown by Salt-Assisted CVD Methods

Chemical synthesis is a compelling alternative to top-downfabricationfor controlling the size, shape, and composition of two-dimensional(2D) crystals. Precision tuning of the 2D crystal structure has broadimplications for the discovery of new phenomena and the reliable implementationof these materials in optoelectronic, photovoltaic, and quantum devices.However, precise and predictable manipulation of the edge structurein 2D crystals through gas-phase synthesis is still a formidable challenge.Here, we demonstrate a salt-assisted low-pressure chemical vapor depositionmethod that enables tuning W metal flux during growth of 2D WSe2 monolayers and, thereby, direct control of their edge structureand optical properties. The degree of structural disorder in 2D WSe2 is a direct function of the W metal flux, which is controlledby adjusting the mass ratio of WO3 to NaCl. This edge disorderthen couples to excitonic disorder, which manifests as broadened andspatially varying emission profiles. Our work links synthetic parameterswith analyses of material morphology and optical properties to providea unified understanding of intrinsic limits and opportunities in synthetic2D materials.