Layer-Dependent Oxidation Spreading in Multilayer Graphene during AFM Local Anodic Oxidation

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Local anodic oxidation is a key technique for creating graphene oxide nanostructures.
• Oxidation spreading from a stationary tip on graphene remains understudied.
• Previous research focused on monolayer graphene, necessitating studies on multilayer systems.

Purpose of the Study:

• To investigate the effect of graphene layer number on oxidation spreading patterns.
• To characterize the different nanostructure types formed.
• To develop a theoretical model for pattern formation.

Main Methods:

• Utilized atomic force microscopy (AFM) for local anodic oxidation and topography.
• Employed Kelvin probe force microscopy and Raman spectroscopy for property characterization.
• Performed electric field calculations using COMSOL Multiphysics for theoretical modeling.

Main Results:

• Identified three distinct pattern categories: graphene craters (2-8 layers), isotropic etching (8-14 layers), and anisotropic etching (>28 layers).
• Observed pattern radius increases with relative humidity, independent of exposure time.
• Correlated pattern formation with oxidation initiated at graphene defects and cleavages.

Conclusions:

• The number of graphene layers significantly influences anodic oxidation spreading patterns.
• Relative humidity plays a crucial role in determining pattern size.
• A combined experimental and simulation model explains the observed phenomena based on defect-initiated oxidation.