Reaction-diffusion study of electron-beam-induced contamination growth

Area of Science:

• Surface science
• Materials science
• Electron microscopy

Background:

• Electron beam irradiation can cause hydrocarbon contamination on surfaces.
• Understanding contaminant dynamics is crucial for high-resolution imaging and material analysis.

Purpose of the Study:

• To develop a time-dependent reaction-diffusion model for electron beam-induced contamination.
• To minimize parameters describing contaminant flow and polymerization.
• To validate the model against experimental data.

Main Methods:

• Developed a reaction-diffusion model incorporating diffusion, polymerization, and residual gas effects.
• Determined model parameters (electron interaction cross-section, diffusion coefficient, initial density, contaminant supply frequency) via experimental comparison.
• Utilized high-angle annular dark-field scanning-transmission electron microscopy (HAADF-STEM) and Monte Carlo simulations for quantification.
• Conducted time-resolved experiments with short intervals up to 20 minutes.

Main Results:

• The model accurately describes the dynamical growth of contamination under electron beam irradiation.
• Experimental data validated the model's ability to capture contaminant flow and polymerization.
• The model successfully predicted contamination growth for non-homogeneous initial conditions.

Conclusions:

• The developed model provides a quantitative understanding of electron beam-induced contamination.
• The findings can inform strategies to mitigate contamination in electron microscopy.
• The dynamic analysis may offer insights into contaminant molecule size.