Selective Oxidation of WS2 Defect Domain with Sub-Monolayer Thickness Leads to Multifold Enhancement in Photoluminescence

摘要

Stabilizing defective domains of sub-monolayer thickness in 2D materials plays a significant role in tuning the electronic and optical properties. The chemical vapor deposition growth of WS2 monolayers with control over phase and uniformly nucleated defect domains is reported. Multifold photoluminescence (PL) enhancement (approximate to 20-fold) is achieved by stabilizing defect-dominated domains toward design of nanoscale optical devices. While the observed luminescence variation in the form of alternating triangles arises from planar heterostructure (1H-1T ') formation, defect domain present at the center of WS2 heterophase monolayer causes 20-fold enhancement in photoluminescence. The observed luminescence enhancement is correlated with sulfur defects and confirmed by site-specific spatial X-ray photoemission spectroscopy and in situ PL measurements at cryogenic temperatures. Detailed microstructural and spectroscopic observations indicate the partial stripping of monolayers by removal of sulfur and incorporation of oxygen leading to increased excitonic emissions. The demonstrated atomic-scale manipulation to stabilize defect domains over large area with enhanced luminescence behavior is relevant for developing next-generation nanoscale photonic devices.