Sampling Depths, Depth Shifts, and Depth Resolutions for Bi(n)(+) Ion Analysis in Argon Gas Cluster Depth Profiles

Area of Science:

• Materials Science
• Analytical Chemistry
• Surface Science

Background:

• Gas cluster sputter depth profiling is vital for analyzing organic materials.
• Understanding sampling depth effects is critical for accurate depth profiling.

Purpose of the Study:

• Investigate sampling depth effects in secondary ion mass spectrometry (SIMS) depth profiling.
• Quantify apparent shifts in depth profiles of organic delta layers.

Main Methods:

• Dual beam mode SIMS depth profiling of Irganox 3114 delta layers in Irganox 1010.
• Sputtering with 5 keV Ar₂₀₀₀⁺ ions.
• Analysis using Bi(q+), Bi₃(q+), and Bi₅(q+) ions (13-50 keV).

Main Results:

• Delta layers broadened from 1 nm to 8-12 nm fwhm.
• Centroid shifts up to 3 nm observed, varying with secondary ion species and energy.
• Shifts correlate linearly with Bi(n)(q+) beam energy, greatest for Bi₃(q+).
• Observed broadening consistent with a falling generation and escape depth distribution function.

Conclusions:

• Sampling depth significantly impacts depth profile accuracy in gas cluster SIMS.
• Low analysis beam energies and large secondary ion fragments are recommended for improved depth measurements.
• Single beam mode analysis may offer an alternative for accurate depth profiling.