Near-field spectral mapping of individual exciton complexes of monolayer WS2 correlated with local defects and charge population

作者：Lee Yongjun; Yun Seok Joon; Kim Youngbum; Kim Min Su; Han Gang Hee; Sood A K; Kim Jeongyong

来源：Nanoscale, 2017, 9(6): 2272-2278.

DOI：10.1039/c6nr08813a

Exciton transitions are mostly responsible for the optical properties of transition metal dichalcogenide monolayers (1L-TMDs). Extensive studies of optical and structural characterization indicated that the presence of local structural defects and charge population critically influence the exciton emissions of 1L-TMDs. However, due to large variations of sample and experimental conditions, the exact mechanism of the exciton emission influenced by local structural defects and charge population is not clearly understood. In this work by using near-field scanning optical imaging and spectroscopy, we directly visualized spatially-and spectrally-resolved emission profiles of excitons, trions and defect bound excitons in CVD-grown monolayer tungsten disulfide (1L-WS2) with similar to 70 nm spatial resolution. We found that exciton emission is spatially uniform while emission of trions and defect bound excitons was strongly modulated by the presence of structural features such as defects and wrinkles. We also visually observe a strong correlation between local charge accumulation and the trion formation upon increased photo-excitation.

• 出版日期2017