Defect healing and charge transfer mediated valley polarization in MoS/MoSe/MoS trilayer van der Waals heterostructures
arXiv:1703.00806 · doi:10.1021/acs.nanolett.7b00904
Abstract
Monolayer transition metal dichalcogenides (TMDC) grown by chemical vapor deposition (CVD) are plagued by a significantly lower optical quality compared to exfoliated TMDC. In this work we show that the optical quality of CVD-grown MoSe is completely recovered if the material is sandwiched in MoS/MoSe/MoS 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 MoS layers are donated to heal Se vacancy defects in the middle MoSe layer. In addition, the trilayer structure exhibits a considerable charge-transfer mediated valley polarization of MoSe 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.
arXiv commentJust accepted for publication in Nano Letters (http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b00904)
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