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Bandstructure engineering using alloying is widely utilised for achieving optimised performance in modern semiconductor devices. While alloying has been studied in monolayer transition metal dichalcogenides, its appli- cation in van der Waals heterostructures built from atomically thin layers is largely unexplored. Here, we fabricate heterobilayers made from mono- layers of WSe2 (or MoSe2) and MoxW1−xSe2 alloy and observe nontrivial tuning of the resultant bandstructure as a function of concentration x. We monitor this evolution by measuring the energy of photolumines- cence (PL) of the interlayer exciton (IX) composed of an electron and hole residing in different monolayers. In MoxW1−xSe2/WSe2, we observe a strong IX energy shift of ≈100 meV for x varied from 1 to 0.6. However, for x < 0.6 this shift saturates and the IX PL energy asymptotically approaches that of the indirect bandgap in bilayer WSe2. We theoretically interpret this observation as the strong variation of the conduction band K valley for x > 0.6, with IX PL arising from the K − K transition, while for x < 0.6, the bandstructure hybridization becomes prevalent leading to the dominating momentum-indirect K-Q transition. This bandstructure hybridization is accompanied with strong modification of IX PL dynam- ics and nonliner exciton properties. Our work provides foundation for bandstructure engineering in van der Waals heterostructures highlighting the importance of hybridization effects and opening a way to devices with accurately tailored electronic properties.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Bandstructure engineering, van der Waals heterostructures, interlayer exciton

Date published: 2024-02-13

Publisher: Wiley

Journal:

• Advanced Materials (ISSN: 15214095) vol. 36 issue. 19 2309644

Funding:

• Engineering and Physical Sciences Research Council EP/V034804/1
• Engineering and Physical Sciences Research Council EP/S030751/1
• Engineering and Physical Sciences Research Council EP/V007033/1
• Horizon 2020 676108
• Horizon 2020 101029644
• Japan Society for the Promotion of Science 20H00354
• Japan Society for the Promotion of Science 21H05233
• Japan Society for the Promotion of Science 23H02052
• Royal Society RSRP\R\190000
• Engineering and Physical Sciences Research Council EP/V006975/1
• Engineering and Physical Sciences Research Council EP/V026496/1
• Engineering and Physical Sciences Research Council EP/S030719/1
• Horizon 2020 785219
• Horizon 2020 881603

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/adma.202309644

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Updated at: 2025-02-26 08:30:39 +0900

Published on MDR: 2025-02-26 08:30:39 +0900