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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
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Summary
This summary is machine-generated.

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.

Keywords:
Coulomb blockadeHfO 2atomic layer depositionhigh- k dielectrictransition metal dichalcogenides

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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.