Journal
ACS NANO
Volume 8, Issue 6, Pages 5738-5745Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn500532f
Keywords
MoS2; photoluminescence; defect engineering; plasma; oxygen bonding; excitons
Categories
Funding
- NSFC [11104026, 11274154, 11225421, 61376104, 21173040, 21373045, 61325020, 61261160499]
- Program for New Century Excellent Talents in University [NCET-11-0094]
- NBRP [2013CBA01600, 2011CB302004, 2010CB923401]
- open research fund of State Key Laboratory of Advanced Optical Communication Systems and Networks, SJTU, China
- Natural Science Foundation of Jiangsu Province [BK2011585, BE2011159, BK20130016]
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We report on a strong photoluminescence (PL) enhancement of monolayer MoS2 through defect engineering and oxygen bonding. Micro-PL and Raman images clearly reveal that the PL enhancement occurs at cracks/defects formed during high-temperature annealing. The PL enhancement at crack/defect sites could be as high as thousands of times after considering the laser spot size. The main reasons of such huge PL enhancement include the following: (1) the oxygen chemical adsorption induced heavy p doping and the conversion from trion to exciton; (2) the suppression of nonradiative recombination of excitons at defect sites, which was verified by low-temperature PL measurements. First-principle calculations reveal a strong binding energy of similar to 2.395 eV for an oxygen molecule adsorbed on a S vacancy of MoS2. The chemically adsorbed oxygen also provides a much more effective charge transfer (0.997 electrons per O-2) compared to physically adsorbed oxygen on an ideal MoS2 surface. We also demonstrate that the defect engineering and oxygen bonding could be easily realized by mild oxygen plasma irradiation. X-ray photoelectron spectroscopy further confirms the formation of Mo-O bonding. Our results provide a new route for modulating the optical properties of two-dimensional semiconductors. The strong and stable PL from defects sites of MoS2 may have promising applications in optoelectronic devices.
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