Investigation of O-18 enriched hematite (α-Fe2O3) by laser assisted atom probe tomography

Quantitative composition measurements of metal-oxides by atom probe tomography (APT) face the problem of the nature of the oxygen peak at 16 Da. Due to a possible overlap between singly charged monomer (O+) and doubly charged dimer (O22+), the contribution of this peak to the total amount of oxygen in the analyzed samples is still matter of debate. In order to study this issue, laser assisted APT was used to analyze hematite (α-Fe2O3) samples containing large amounts of oxygen 18. Peak identification reveals that only singly charged monomers (O+) are detected, and that oxygen in detected water molecules does not originate from the oxide samples. With this information, composition of hematite measured by APT is found to be close, but not equal to the expected stoichiometry.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (179 K)Download as PowerPoint slideHighlights► Laser assisted atom probe tomography analysis of hematite (α-Fe2O3). ► Quantification of oxygen content using 18O enriched samples to solve the ambiguity of overlap between O+ and O22+ at 16 Da. ► Evidence given that only singly charged monomers (O+) contributes to the peak at 16 Da.