Reduction of multiple hits in atom probe tomography.

Area of Science:

• Materials Science
• Analytical Chemistry
• Surface Science

Background:

• Atom probe tomography (APT) compositional accuracy is limited by undetected multiple ion hits.
• Multiple hits cause preferential loss of elements that field evaporate in bursts or as molecules.
• This issue particularly affects the analysis of materials like carbides.

Purpose of the Study:

• To explore a method for reducing the impact of multiple hits in APT.
• To improve the accuracy of compositional measurements in APT analyses.

Main Methods:

• A fine metal grid was implemented as a filter behind the local electrode.
• The grid reduced the overall detection efficiency from 37% to approximately 5%.
• Multiple hit characteristics were compared with and without the grid filter.

Main Results:

• The fraction of ions originating from multiple hits decreased from 46% to 10% in tungsten carbide analysis.
• Measured carbon concentration in tungsten carbide improved from 48.2 at% to 49.8 at%, nearing the expected 50.0 at%.
• The grid filter effectively reduced the occurrence of multiple ion detection events.

Conclusions:

• Implementing a grid filter is an effective strategy to mitigate multiple hit artifacts in APT.
• This method significantly enhances the accuracy of compositional analysis, especially for challenging samples.
• The reduced multiple hits lead to more reliable elemental quantification in APT.