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Published on: August 2, 2019
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Gate-Defined Quantum Confinement in CVD 2D WS2
Chit Siong Lau1, Jing Yee Chee1, Liemao Cao2
1Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore.
Advanced Materials (Deerfield Beach, Fla.)
|August 26, 2021
Summary
Interface roughness, not charge impurities, limits carrier mobility in WS2 devices. Atomic layer deposition of HfO2 enables quantum confinement, paving the way for quantum information processing applications.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Transition metal dichalcogenides like WS2 are promising for electronic and quantum applications.
- Understanding factors limiting carrier mobility is crucial for device optimization.
- Atomic layer deposition (ALD) is a key technique for thin-film fabrication.
Purpose of the Study:
- To investigate the impact of HfO2 ALD on the low-temperature carrier transport of WS2.
- To identify the dominant factor limiting carrier mobility in WS2 devices.
- To demonstrate electrostatic gate-defined quantum confinement in WS2 using HfO2.
Main Methods:
- Temperature-dependent transport measurements on CVD-grown WS2 before and after HfO2 ALD.
- Characterization using circular dichroic photoluminescence spectroscopy and X-ray photoemission spectroscopy.
- Microscopy (cross-sectional scanning transmission electron microscopy) and theoretical modeling (DFT, transport modeling).
Main Results:
- Interface roughness, not charge impurities, was identified as the primary limitation for carrier mobility.
- HfO2 deposition did not degrade carrier transport; its high dielectric constant and low leakage were beneficial.
- Demonstrated electrostatic quantum confinement in WS2/HfO2 structures, achieving quantum dot sizes as small as 58 nm.
Conclusions:
- Interface roughness is a critical, often overlooked, factor in WS2 transport properties.
- ALD-grown HfO2 is a suitable dielectric for scalable WS2 device fabrication.
- The demonstrated quantum confinement approach is vital for advancing WS2 in quantum information processing.
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