Understanding Fragmentation of Organic Small Molecules in Atom Probe Tomography.

Area of Science:

• Materials Science
• Chemistry
• Physics

Background:

• Atom probe tomography (APT) is a powerful surface-sensitive technique for materials analysis.
• Field ionization in APT of organic materials can lead to molecular fragmentation, complicating analysis.
• The underlying mechanisms of this fragmentation have not been well understood.

Purpose of the Study:

• To elucidate the mechanism governing the fragmentation of doubly ionized small molecule organic materials during atom probe tomography.
• To identify predictive factors for post-ionization fragmentation in organic materials analyzed by APT.

Main Methods:

• Utilized density functional theory (DFT) to compute molecular geometries and free energies.
• Analyzed the relationship between computed molecular properties and observed fragmentation events in APT.

Main Results:

• Fragmentation of parent molecular dications into daughter ions is predictable based on computed molecular properties.
• Exergonic free energies for daughter ion formation, lower activation energies for dissociation, and increased bond lengths are quantitative predictors of fragmentation.
• The findings provide a mechanistic explanation for observed fragmentation patterns.

Conclusions:

• This research provides a fundamental understanding of molecular fragmentation in APT of organic materials.
• The identified predictive factors enhance the applicability and interpretation of APT for complex organic systems.
• This work bridges a gap in understanding APT processes for molecular and organic materials.