Damage-Free Atomic Layer Etch of WSe₂: A Platform for Fabricating Clean Two-Dimensional Devices

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Controlling layer thickness and patterning of 2D materials is vital for device performance.
• Conventional etching methods are often unsuitable for delicate 2D materials due to their atomic thinness and structural similarity.

Purpose of the Study:

• To develop a controllable, selective, and damage-free atomic layer etch (ALE) process for monolayer 2D materials.
• To demonstrate the preservation of physical, optical, and electronic properties after ALE.
• To showcase the fabrication of high-performance 2D devices using ALE and a novel sacrificial layer technique.

Main Methods:

• A top-down atomic layer etch (ALE) process involving self-limited oxidation and selective removal.
• Comprehensive material, optical, and electrical characterization (e.g., photoluminescence, mobility measurements).
• Development and application of the Sacrificial WSe2 with ALE Processing (SWAP) technique for device fabrication.

Main Results:

• Achieved layer-by-layer removal of monolayer WSe2 using ALE without damaging underlying layers.
• ALE-processed WSe2 retained excellent photoluminescence and high room-temperature hole mobility (515 cm²/V·s).
• Graphene transistors fabricated using the SWAP technique exhibited ultra-high room-temperature field-effect mobilities (up to 200,000 cm²/V·s).

Conclusions:

• The developed ALE process is effective for precise and damage-free etching of 2D materials.
• ALE-processed WSe2 is suitable for high-performance 2D electronic device applications.
• The SWAP technique offers a promising route for fabricating advanced 2D devices with superior performance.