Abstract
Janus transition-metal dichalcogenide monolayers are artificial materials, where one plane of chalcogen atoms is replaced by chalcogen atoms of a different type. Theory predicts an in-built out-of-plane electric field, giving rise to long-lived, dipolar excitons, while preserving direct-bandgap optical transitions in a uniform potential landscape. Previous Janus studies had broad photoluminescence (>18 meV) spectra obfuscating their specific excitonic origin. Here, we identify the neutral and the negatively charged inter- and intravalley exciton transitions in Janus WSeS monolayers with ∼6 meV optical line widths. We integrate Janus monolayers into vertical heterostructures, allowing doping control. Magneto-optic measurements indicate that monolayer WSeS has a direct bandgap at the K points. Our results pave the way for applications such as nanoscale sensing, which relies on resolving excitonic energy shifts, and the development of Janus-based optoelectronic devices, which requires charge-state control and integration into vertical heterostructures.
Original language | English (US) |
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Pages (from-to) | 7326-7334 |
Number of pages | 9 |
Journal | ACS nano |
Volume | 17 |
Issue number | 8 |
DOIs | |
State | Published - Apr 25 2023 |
Keywords
- 2D materials
- Janus transition-metal dichalcogenides
- W monolayers
- charge tunable
- excitons
- layered materials
ASJC Scopus subject areas
- General Materials Science
- General Engineering
- General Physics and Astronomy