Atomic Layer Etching Mechanism of MoS₂ for Nanodevices

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Molybdenum disulfide (MoS2) is a 2D material with tunable electronic properties.
• Controlling MoS2 layer thickness is crucial for electronic and optoelectronic applications.
• Existing methods for thinning MoS2 can cause damage and contamination.

Purpose of the Study:

• To develop a precise and damage-free method for thinning MoS2 layers.
• To elucidate the atomic layer etching (ALE) mechanism for MoS2.
• To demonstrate the effectiveness of ALE for fabricating high-quality monolayer MoS2 devices.

Main Methods:

• Atomic Layer Etching (ALE) using chlorine (Cl) radicals for adsorption and low-energy argon (Ar+) ions for desorption.
• Experimental characterization and simulation to understand the MoS2 ALE mechanism.
• Fabrication and electrical testing of monolayer MoS2 field-effect transistors (FETs) after ALE.

Main Results:

• A sequential etching mechanism for MoS2 ALE involving S(top), Mo(mid), and S(bottom) layers was identified.
• ALE effectively removes MoS2 layers without inducing significant damage or contamination.
• Monolayer MoS2 FETs fabricated using ALE exhibit excellent electrical properties comparable to pristine devices.

Conclusions:

• Atomic layer etching (ALE) is a highly effective technique for controlled thinning of MoS2.
• The developed ALE process preserves the structural integrity and electrical performance of MoS2.
• This ALE technique is applicable to other layered transition metal dichalcogenides (TMDs).