Monolayer transition metal dichalcogenides (TMDCs) grown by chemical vapor deposition (CVD) are plagued by a significantly lower optical quality compared to exfoliated TMDCs. In this work, we show that the optical quality of CVD-grown MoSe2 is completely recovered if the material is sandwiched in MoS2/MoSe2/MoS2 trilayer van der Waals heterostructures. We show by means of density functional theory that this remarkable and unexpected result is due to defect healing: S atoms of the more reactive MoS2 layers are donated to heal Se vacancy defects in the middle MoSe2 layer. In addition, the trilayer structure exhibits a considerable charge-transfer mediated valley polarization of MoSe2 without the need for resonant excitation. Our fabrication approach, relying solely on simple flake transfer technique, paves the way for the scalable production of large-area TMDC materials with excellent optical quality.
Bibliographical noteFunding Information:
This work was partially supported by ANR JCJC project milliPICS the Region Midi-Pyrenees under contract MESR 13053031, BLAPHENE project under IDEX program Emergence, Programme des Investissements d'Avenir under the program ANR-11-IDEX-0002-02 reference ANR-10-LABX-0037-NEXT, Swiss SNF Sinergia Grant 147607 the European Commission (ITN MoWSeS, GA 317451), and Deutsche Forschungsgemeinschaft (HE 3543/27-1 and GRK 2247/1 (QM3)).
© 2017 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering