Electron Beam-Induced Carbon Erosion and the Impact on Electron Probe Microanalysis

Area of Science:

• Materials Science
• Surface Science
• Analytical Chemistry

Background:

• Electron beam-induced carbon contamination is a complex process involving simultaneous deposition and erosion.
• Accurate quantification in electron microscopy relies on understanding and mitigating such contamination effects.

Purpose of the Study:

• To quantify electron beam-induced carbon erosion rates on carbon-coated bismuth (Bi) substrates.
• To investigate the influence of electron beam parameters (flux density, accelerating voltage) on erosion.
• To assess the impact of carbon erosion on coating and substrate quantification and propose correction methods.

Main Methods:

• Measurements were performed on carbon-coated Bi substrates (5-20 nm thickness) under varying electron beam conditions (25 nA, 3 kV).
• Electron flux density and accelerating voltage were systematically varied.
• Time-dependent intensity (TDI) measurements were utilized for error correction.

Main Results:

• Net erosion rates were determined, with a 5 nm C coating reduced by 20% in 60 s at 25 nA, 3 kV.
• Erosion increased with electron flux density and decreased accelerating voltage.
• Uncorrected analyses showed significant errors in coating thickness and Bi Mα quantification, particularly at lower voltages and thinner coatings.

Conclusions:

• Electron beam-induced carbon erosion is a critical factor affecting quantitative analysis in electron microscopy.
• Time-dependent intensity (TDI) measurements offer a viable method to correct for carbon erosion-induced errors.
• Optimizing accelerating voltage and understanding flux density are essential for minimizing quantification errors in C-coated Bi samples.