Remote epitaxy of single-crystal rhombohedral WS2 bilayers
Chao Chang1,2, Xiaowen Zhang1,2, Weixuan Li1,2
1Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics, South China Normal University, Guangzhou, 510006, China.
Nature Communications
|May 16, 2024
Summary
Researchers developed a method for growing centimeter-scale, single-crystal rhombohedral-stacked (R-stacked) tungsten disulfide (WS2) bilayer films. This controlled stacking significantly enhances electrical performance and optical properties compared to monolayer films.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Rhombohedral-stacked (R-stacked) transition metal dichalcogenide (TMD) bilayers offer superior properties over monolayers, including enhanced electrical and optical performance.
- Thermodynamic similarity between R-stacked and hexagonal-stacked (H-stacked) TMD bilayers leads to mixed stacking in epitaxial films, hindering controlled synthesis.
- Achieving pure R-stacked TMD bilayers is crucial for harnessing their unique electronic and optical functionalities.
Purpose of the Study:
- To develop a method for the remote epitaxy of centimeter-scale, single-crystal R-stacked WS2 bilayer films.
- To understand and control the stacking configuration during the growth of TMD bilayers.
- To investigate the enhanced properties of R-stacked WS2 bilayers compared to monolayer films.
Main Methods:
- Utilizing remote epitaxy on sapphire substrates with controlled high flux tungsten source feeding at high temperatures.
- Leveraging symmetry breaking in a-plane sapphire to influence atomic steps and control the R-stacking of the upper TMD layer.
- Characterizing the grown films for structural, electrical, and optical properties.
Main Results:
- Successfully grew centimeter-scale single-crystal R-stacked WS2 bilayer films.
- Observed up to 30-fold enhancement in carrier mobility (34 cm2V-1s-1) compared to monolayer films.
- Achieved nearly doubled circular helicity (61%) and confirmed interfacial ferroelectricity in the R-stacked bilayers.
Conclusions:
- A growth mechanism for stacking-controlled bilayer TMD single crystals has been established.
- The developed method enables the large-scale production of R-stacked TMD materials.
- The enhanced properties of R-stacked WS2 bilayers open avenues for advanced electronic and optoelectronic applications.
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