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Abstract Two-dimensional (2D) semiconductors are promising candidates for optoelectronic application and quantum information processes due to their inherent out-of-plane 2D confinement. In addition, they offer the possibility of achieving low-dimensional in-plane exciton confinement, similar to zero-dimensional quantum dots, with intriguing optical and electronic properties via strain or composition engineering. However, realizing such laterally confined 2D monolayers and systematically controlling size-dependent optical properties remain significant challenges. Here, we report the observation of lateral confinement of excitons in epitaxially grown in-plane MoSe2quantum dots (~15-60 nm wide) inside a continuous matrix of WSe2monolayer film via a sequential epitaxial growth process. Various optical spectroscopy techniques reveal the size-dependent exciton confinement in the MoSe2monolayer quantum dots with exciton blue shift (12-40 meV) at a low temperature as compared to continuous monolayer MoSe2. Finally, single-photon emission (g2(0) ~ 0.4) was also observed from the smallest dots at 1.6 K. Our study opens the door to compositionally engineered, tunable, in-plane quantum light sources in 2D semiconductors.
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Trifluoromethylation of 2D Transition Metal Dichalcogenides: A Mild Functionalization and Tunable p‐Type Doping Method
Abstract Chemical modification is a powerful strategy for tuning the electronic properties of 2D semiconductors. Here we report the electrophilic trifluoromethylation of 2D WSe2and MoS2under mild conditions using the reagent trifluoromethyl thianthrenium triflate (TTT). Chemical characterization and density functional theory calculations reveal that the trifluoromethyl groups bind covalently to surface chalcogen atoms as well as oxygen substitution sites. Trifluoromethylation induces p‐type doping in the underlying 2D material, enabling the modulation of charge transport and optical emission properties in WSe2. This work introduces a versatile and efficient method for tailoring the optical and electronic properties of 2D transition metal dichalcogenides.
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- Award ID(s):
- 2223922
- PAR ID:
- 10557751
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 63
- Issue:
- 22
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The ongoing reduction in transistor sizes drives advancements in information technology. However, as transistors shrink to the nanometer scale, surface and edge states begin to constrain their performance. 2D semiconductors like transition metal dichalcogenides (TMDs) have dangling‐bond‐free surfaces, hence achieving minimal surface states. Nonetheless, edge state disorder still limits the performance of width‐scaled 2D transistors. This work demonstrates a facile edge passivation method to enhance the electrical properties of monolayer WSe2nanoribbons, by combining scanning transmission electron microscopy, optical spectroscopy, and field‐effect transistor (FET) transport measurements. Monolayer WSe2nanoribbons are passivated with amorphous WOxSeyat the edges, which is achieved using nanolithography and a controlled remote O2plasma process. The same nanoribbons, with and without edge passivation are sequentially fabricated and measured. The passivated‐edge nanoribbon FETs exhibit 10 ± 6 times higher field‐effect mobility than the open‐edge nanoribbon FETs, which are characterized with dangling bonds at the edges. WOxSeyedge passivation minimizes edge disorder and enhances the material quality of WSe2nanoribbons. Owing to its simplicity and effectiveness, oxidation‐based edge passivation could become a turnkey manufacturing solution for TMD nanoribbons in beyond‐silicon electronics and optoelectronics.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/anie.202403494
