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Twist-Angle-Dependent Optoelectronics in a Few-Layer Transition-Metal Dichalcogenide Heterostructure
Woosuk Choi, Imtisal Akhtar, Malik Abdul Rehman
1Department of Physics , Sogang University , Seoul 04107 , Korea.
ACS Applied Materials & Interfaces
|December 19, 2018
Summary
Lattice mismatch in WSe2/MoSe2 heterostructures creates a potential barrier, affecting device performance. However, light illumination enables current flow, with untwisted devices showing higher IR sensitivity.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Vertical heterostructures (HS) are crucial for electronic devices.
- Lattice matching is hypothesized to influence coupling and device performance.
- Understanding interlayer coupling is key for novel electronic and optoelectronic applications.
Purpose of the Study:
- To investigate the role of lattice matching in the coupling of p-type WSe2 and n-type MoSe2 in vertical heterostructures.
- To analyze the impact of varying crystal orientation angles (twist angles) on heterojunction properties.
- To explore the influence of illumination on device behavior under different lattice matching conditions.
Main Methods:
- Fabrication of WSe2/MoSe2 heterojunction devices with twist angles of 0°, 15°, and 30°.
- Estimation of crystal orientations using high-resolution X-ray diffraction.
- Characterization of device performance via I-V curves, spectral responsivity, external quantum efficiency, photoluminescence, and Raman spectroscopy.
Main Results:
- A well-established p-n junction with strong coupling was observed in the 0° twist angle sample due to lattice matching.
- Lattice mismatch in 15° and 30° twisted samples created a van der Waals gap and a potential barrier.
- Under 365 nm illumination, current flowed in both directions across the potential barrier in twisted samples.
- Untwisted heterostructures showed higher sensitivity to infrared illumination, while UV illumination effects were minimal across twist angles.
- Photoluminescence and Raman spectroscopy confirmed weak coupling in twisted heterostructures due to lattice mismatch.
Conclusions:
- Lattice matching significantly influences the interlayer coupling and junction behavior in WSe2/MoSe2 vertical heterostructures.
- Twist angle-induced lattice mismatch leads to potential barriers that can be overcome by photoexcitation.
- Device sensitivity to illumination is dependent on both lattice orientation and the wavelength of light.
Keywords:
a few-layer TMDheterostructureoptoelectronicsp−n junctiontransition-metal dichalcogenidestwist angleMore Related Videos
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