期刊
NANO LETTERS
卷 20, 期 4, 页码 2544-2550出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.9b05323
关键词
Transition metal dichalcogenides (TMDCs); two-dimensional (2D) semiconductors; low-temperature photoluminescence; defect-bound excitons
类别
资金
- Deutsche Forschungsgemeinschaft (DFG) [182087777 - SFB 951]
- ERC [639739]
- European Research Council (ERC) [639739] Funding Source: European Research Council (ERC)
We investigate the excitonic peak associated with defects and disorder in low-temperature photoluminescence of monolayer transition metal dichalcogenides (TMDCs). To uncover the intrinsic origin of defect-related (D) excitons, we study their dependence on gate voltage, excitation power, and temperature in a prototypical TMDC monolayer MoS2. Our results suggest that D excitons are neutral excitons bound to ionized donor levels, likely related to sulfur vacancies, with a density of 7 x 10(11) cm(-2). To study the extrinsic contribution to D excitons, we controllably deposit oxygen molecules in situ onto the surface of MoS2 kept at cryogenic temperature. We find that, in addition to trivial p-doping of 3 x 10(12) cm(-2), oxygen affects the D excitons, likely by functionalizing the defect sites. Combined, our results uncover the origin of D excitons, suggest an approach to track the functionalization of TMDCs, to benchmark device quality, and pave the way toward exciton engineering in hybrid organic-inorganic TMDC devices.
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