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Article Dans Une Revue npj 2D Materials and Applications Année : 2021

Indirect to direct band gap crossover in two-dimensional WS2(1−x)Se2x alloys

Debora Pierucci
Biyuan Zheng
  • Fonction : Auteur
José Avila
  • Fonction : Auteur
Pavel Dudin
Julien Chaste
Marco Pala
Thibault Brulé
  • Fonction : Auteur
Anlian Pan
  • Fonction : Auteur

Résumé

In atomically thin transition metal dichalcogenide semiconductors, there is a crossover from indirect to direct band gap as the thickness drops to one monolayer, which comes with a fast increase of the photoluminescence signal. Here, we show that for different alloy compositions of WS2(1−x)Se2x this trend may be significantly affected by the alloy content and we demonstrate that the sample with the highest Se ratio presents a strongly reduced effect. The highest micro-PL intensity is found for bilayer WS2(1−x)Se2x (x = 0.8) with a decrease of its maximum value by only a factor of 2 when passing from mono-layer to bi-layer. To better understand this factor and explore the layer-dependent band structure evolution of WS2(1−x)Se2x, we performed a nano-angle-resolved photoemission spectroscopy study coupled with first-principles calculations. We find that the high micro-PL value for bilayer WS2(1−x)Se2x (x = 0.8) is due to the overlay of direct and indirect optical transitions. This peculiar high PL intensity in WS2(1−x)Se2x opens the way for spectrally tunable light-emitting devices.
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Dates et versions

hal-03450806 , version 1 (26-11-2021)

Identifiants

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Cyrine Ernandes, Lama Khalil, Hela Almabrouk, Debora Pierucci, Biyuan Zheng, et al.. Indirect to direct band gap crossover in two-dimensional WS2(1−x)Se2x alloys. npj 2D Materials and Applications, 2021, 5, pp.7. ⟨10.1038/s41699-020-00187-9⟩. ⟨hal-03450806⟩
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