Controlled Layer-by-Layer Etching of MoS₂.

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Two-dimensional (2D) materials like molybdenum disulfide (MoS2) are promising for next-generation electronics beyond complementary metal-oxide-semiconductor (CMOS) technology.
• Achieving high-performance devices requires precise control over material thickness at the atomic level.

Purpose of the Study:

• To introduce and validate a novel atomic layer etching (ALET) technique for the precise, layer-by-layer thinning of molybdenum disulfide (MoS2).
• To demonstrate the capability of ALET in controlling the number of MoS2 layers for advanced device fabrication.

Main Methods:

• Utilized a cyclic process combining chlorine (Cl)-radical adsorption and argon (Ar)(+) ion-beam desorption for etching MoS2.
• Investigated the etching mechanism by analyzing the effects of individual steps (Cl-radical adsorption, low-energy Ar(+) ion bombardment) and the sequential ALET process.
• Employed Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) to characterize the etched MoS2 layers.

Main Results:

• The sequential ALET process successfully etched one monolayer of MoS2 per cycle.
• Individual steps of Cl-radical adsorption or low-energy Ar(+) ion bombardment alone did not result in MoS2 etching.
• Characterization confirmed the precise removal of one monolayer per cycle, with no significant damage or residue observed on the remaining MoS2 surface.

Conclusions:

• Atomic layer etching (ALET) provides a viable method for the precise, layer-by-layer thinning of molybdenum disulfide (MoS2).
• This technique enables accurate control over MoS2 film thickness, essential for developing advanced beyond-CMOS electronic devices.
• The ALET process is non-damaging and leaves no residue, ensuring material integrity for device applications.