The Role of Oxygen Atoms on Excitons at the Edges of Monolayer WS<sub>2</sub> Zhenliang Hu Jose Avila Xinyun Wang Jin Feng Leong Qi Zhang Yanpeng Liu Maria C. Asensio Junpeng Lu Alexandra Carvalho Chorng Haur Sow Antonio Helio Castro Neto 10.1021/acs.nanolett.9b01670.s001 https://acs.figshare.com/articles/journal_contribution/The_Role_of_Oxygen_Atoms_on_Excitons_at_the_Edges_of_Monolayer_WS_sub_2_sub_/8289176 We clarify that the chemisorption of oxygen atoms at the edges is a key contributor to the frequently observed edge enhancement and spatial non-uniformities of photoluminescence (PL) in WS<sub>2</sub> monolayers. Here we have investigated with momentum- and real-space nanoimaging of the chemical and electronic density inhomogeneity of WS<sub>2</sub> flakes. Our finding from a large panoply of techniques together with density functional theory calculation confirms that the oxygen chemisorption leads to the electron accumulation at the edges. This facilitates the trion dominance of PL at the edges of WS<sub>2</sub> flakes. Our results highlight and unravel the significance of chemisorbed oxygen at the edges in the PL emission and electronic structure of WS<sub>2</sub>, providing a viable path to enhance the performance of transition-metal-dichalcogenide-based devices. 2019-06-12 00:00:00 WS 2 electron accumulation oxygen chemisorption real-space nanoimaging Oxygen Atoms chemisorbed oxygen density inhomogeneity edge enhancement theory calculation trion dominance Monolayer WS 2 oxygen atoms WS 2 flakes PL emission transition-metal-dichalcogenide-based devices WS 2 monolayers