Sputtering Yields for Mixtures of Organic Materials Using Argon Gas Cluster Ions

Area of Science:

• Materials Science
• Surface Science
• Analytical Chemistry

Background:

• Sputtering yield is a critical parameter in surface analysis and thin film processing.
• Binary mixtures can exhibit complex sputtering behaviors deviating from ideal mixing models.
• Matrix effects in secondary ion mass spectrometry (SIMS) can significantly impact depth profiling accuracy.

Purpose of the Study:

• To measure sputtering yield volumes for binary mixtures of Irganox 1010 with Irganox 1098 and Fmoc-pentafluoro-L-phenylalanine (FMOC).
• To investigate the influence of matrix effects on sputtering yield measurements.
• To evaluate the applicability of linear interpolation models for predicting sputtering yields of mixtures.

Main Methods:

• Sputtering yield measurements using 5 keV Ar2000(+) ions at a 45° incident angle.
• Depth profiling of 100 nm thick intimately mixed layers.
• Secondary ion mass spectrometry (SIMS) analysis, with careful selection of secondary ions to mitigate matrix effects.

Main Results:

• Sputtering yield volumes for the binary mixtures were lower than predicted by linear interpolation from pure components.
• Observed profile shifts of up to 15 nm due to matrix effects, leading to potential errors exceeding 20% in deduced sputtering yields.
• Both Irganox 1010/Irganox 1098 and Irganox 1010/FMOC mixtures showed similar trends, with stronger matrix effects noted for the Irganox 1010/FMOC system.

Conclusions:

• The observed reduction in sputtering yield volumes is consistent with a model considering changes in absorbed energy within intimate mixtures.
• Matrix effects play a significant role in the sputtering behavior and depth profiling of these binary mixtures.
• Linear interpolation is insufficient for accurately predicting sputtering yields of these complex organic mixtures.