Remote Plasma Oxidation and Atomic Layer Etching of MoS2

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Molybdenum disulfide (MoS2) is a promising 2D material with unique electronic properties.
• Controlled surface modification of MoS2 is crucial for its integration into electronic devices.
• Understanding oxidation mechanisms is key to preventing degradation and enabling functionalization.

Purpose of the Study:

• To investigate the chemical oxidation of exfoliated MoS2 using remote O2 plasma.
• To characterize the surface changes, structural integrity, and chemical composition during oxidation.
• To explore the potential of remote O2 plasma for MoS2 surface functionalization and controlled thinning.

Main Methods:

• Remote O2 plasma exposure at varying durations and temperatures.
• Surface characterization using X-ray photoelectron spectroscopy (XPS).
• Structural and topographical analysis via low energy electron diffraction (LEED) and atomic force microscopy (AFM).
• Scanning tunneling microscopy (STM) for detailed structural verification.

Main Results:

• Oxidation occurs in a layered manner, primarily affecting the topmost layer of MoS2.
• Formation of S-O bonds and MoOx (molybdenum oxide) layers observed.
• Uniform monolayer amorphous MoO3 forms after 5 min of plasma exposure at 200 °C.
• Annealing at 500 °C effectively removes the MoO3 layer, restoring the ordered MoS2 structure.

Conclusions:

• Remote O2 plasma provides a controllable method for MoS2 surface oxidation.
• This process allows for surface functionalization and precise thinning of MoS2 layers.
• The ability to remove the oxide layer makes it suitable for MoS2 device fabrication processes.