Probing exciton dispersions of freestanding monolayer WSe2 by momentum resolved electron energy loss spectroscopy
Jinhua Hong, Ryosuke Senga, Thomas Pichler, Kazu Suenaga
TL;DR
This study uses momentum-resolved electron energy-loss spectroscopy to measure exciton dispersions in freestanding monolayer WSe2, revealing a new sub-gap exciton linked to selenium vacancies.
Contribution
It introduces a novel application of momentum-resolved EELS to directly probe exciton dispersions in 2D materials, discovering a sub-gap exciton associated with vacancies.
Findings
Observation of parabolic valley exciton dispersions
First detection of a sub-gap dispersive exciton in WSe2
Linking sub-gap exciton to selenium vacancies
Abstract
Momentum resolved electron energy-loss spectroscopy was used to measure the dispersions of excitons in a free-standing monolayer of WSe2. Besides the parabolically dispersed valley excitons, a sub-gap dispersive exciton was observed at specific q values for the first time. The simultaneous STEM-ADF imaging of the local probed areas suggests that this sub-gap exciton is attributed to the prolific Se vacancies.
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