Issue 6, 2017

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

Abstract

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 ∼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.

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

Supplementary files

Article information

Article type
Paper
Submitted
11 Nov 2016
Accepted
12 Jan 2017
First published
13 Jan 2017

Nanoscale, 2017,9, 2272-2278

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

Y. Lee, S. J. Yun, Y. Kim, M. S. Kim, G. H. Han, A. K. Sood and J. Kim, Nanoscale, 2017, 9, 2272 DOI: 10.1039/C6NR08813A

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