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HL: Fachverband Halbleiterphysik

HL 38: 2D materials: Chalcogenides II (joint session HL/DS)

HL 38.7: Vortrag

Donnerstag, 15. März 2018, 11:00–11:15, A 151

Doping dependent photoluminescence of ML WSe2 — Jhih-Sian Tu, •Sven Borghardt, Detlev Grützmacher, and Beata Kardynał — Peter Grünberg Institute 9 (PGI-9), Forschungszentrum Jülich, Germany

While free exciton states of monolayer transistion meatal dichalcogenides are well understood, photoluminescence spectra of WSe_2 contain number of low energy features that are not understood and collectively referred to as localized states. Such signal is not observed in spectra of materials with the lowest energy state being bright for example in the spectra of monolayer MoSe_2. In order to shed light on the origin of the sub-bandgap emission from WSe_2, we measured low temperature photoluminescence at a very wide range of both electron and hole doping levels. The spectra appear rich in structure which is very strongly doping dependent. The spectral, polarization and spatial correlations between the long wavelength emission features with the signal from the recombination of the bright exciton and trion states are consistent with the brightening of momentum-dark states either by phonon-mediated processes or by interactions of excitons with electrons or plasmons. Unexpectedly, while majority of the spectral features share polarization properties of excitons and trions, some show cross-polarization with the excitation laser.