10.1021/nn403682r.s001
Liangxu Lin
Liangxu
Lin
Yaoxian Xu
Yaoxian
Xu
Shaowei Zhang
Shaowei
Zhang
Ian M. Ross
Ian M.
Ross
Albert C. M. Ong
Albert
C. M. Ong
Dan A. Allwood
Dan A.
Allwood
Fabrication of Luminescent Monolayered Tungsten Dichalcogenides Quantum Dots with Giant Spin-Valley Coupling
American Chemical Society
2016
quantum information technology
monolayered tungsten dichalcogenide
contrast bioimaging application
conduction band
split valence band energy levels
flake precursors
570 meV
PL
monolayered WS 2 sheets
WS 2 flakes
UV
Luminescent Monolayered Tungsten Dichalcogenides Quantum Dots
luminescence peaks
defect level
monolayered WS 2 QDs
optoelectronic devices
room temperature
2016-02-18 20:27:06
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Fabrication_of_Luminescent_Monolayered_Tungsten_Dichalcogenides_Quantum_Dots_with_Giant_Spin_Valley_Coupling/2374159
A high yield (>36 wt %) method has been developed of preparing monolayered tungsten dichalcogenide (WS<sub>2</sub>) quantum dots (QDs) with lateral size ∼8–15 nm from multilayered WS<sub>2</sub> flakes. The monolayered WS<sub>2</sub> QDs are, like monolayered WS<sub>2</sub> sheets, direct semiconductors despite the flake precursors being an indirect semiconductor. However, the QDs have a significantly larger direct transition energy (3.16 eV) compared to the sheets (2.1 eV) and enhanced photoluminescence (PL; quantum yield ∼4%) in the blue-green spectral region at room temperature. UV/vis measurements reveal a giant spin-valley coupling of the monolayered WS<sub>2</sub> QDs at around 570 meV, which is larger than that of monolayered WS<sub>2</sub> sheets (∼400 meV). This spin-valley coupling was further confirmed by PL as direct transitions from the conduction band minimum to split valence band energy levels, leading to multiple luminescence peaks centered at around 369 (3.36 eV) and 461 nm (2.69 eV, also contributed by a new defect level). The discovery of giant spin-valley coupling and the strong luminescence of the monolayered WS<sub>2</sub> QDs make them potentially of interests for the applications in semiconductor-based spintronics, conceptual valley-based electronics, quantum information technology and optoelectronic devices. However, we also demonstrate that the fabricated monolayered WS<sub>2</sub> QDs can be a nontoxic fluorescent label for high contrast bioimaging application.