Intrinsic and Extrinsic Defect-Related Excitons in TMDCs.
basic_science · Level V
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- Record sourced from PubMed, PMID 32191482.
- Also identified by DOI 10.1021/acs.nanolett.9b05323.
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Abstract
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 MoS<sub>2</sub>. Our results suggest that D excitons are neutral excitons bound to ionized donor levels, likely related to sulfur vacancies, with a density of 7 × 10<sup>11</sup> cm<sup>-2</sup>. To study the extrinsic contribution to D excitons, we controllably deposit oxygen molecules <i>in situ</i> onto the surface of MoS<sub>2</sub> kept at cryogenic temperature. We find that, in addition to trivial p-doping of 3 × 10<sup>12</sup> cm<sup>-2</sup>, 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.