Probing charge transfer excitons in a MoSe2-WS2 van der Waals heterostructure
Frank Ceballos1, Matthew Z Bellus, Hsin-Ying Chiu
1Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045, USA. huizhao@ku.edu.
Nanoscale
|October 8, 2015
Summary
The MoSe2/WS2 van der Waals heterostructure exhibits unique excitonic states. Charge transfer excitons show a long lifetime and high diffusion, comparable to individual excitons in transition metal dichalcogenides.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Van der Waals heterostructures, such as those combining molybdenum diselenide (MoSe2) and tungsten disulfide (WS2), are promising for advanced electronic and optoelectronic applications.
- Understanding excitonic behavior in these layered materials is crucial for harnessing their unique quantum properties.
Purpose of the Study:
- To investigate the properties and dynamics of excitonic states in a MoSe2/WS2 van der Waals heterostructure.
- To characterize the charge transfer exciton states and their behavior at room temperature.
Main Methods:
- Photoluminescence (PL) spectroscopy was employed to identify and analyze the energy levels of excitonic states.
- Femtosecond transient absorption spectroscopy was utilized to probe the ultrafast dynamics of charge transfer excitons.
Main Results:
- Near-degenerate interlayer and intralayer excitonic states were observed in the MoSe2/WS2 heterostructure.
- Charge transfer exciton states were found to be approximately 50 meV below MoSe2 exciton states, with significant spectral overlap.
- A charge transfer exciton lifetime of approximately 80 picoseconds (ps) and a diffusion coefficient of about 14 cm²/s were determined at room temperature.
Conclusions:
- The MoSe2/WS2 van der Waals heterostructure hosts distinct charge transfer excitons with properties relevant for optoelectronic devices.
- The observed exciton dynamics, including lifetime and diffusion, are comparable to those of individual excitons in transition metal dichalcogenides, highlighting the potential of such heterostructures.
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