Insights into secondary ion formation during dynamic SIMS analysis: Evidence from sputtering of laboratory synthesized uranium compounds with a high-energy O− primary beam on a NanoSIMS 50L

Journal Article · Wed Sep 01 00:00:00 EDT 2021 · Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

DOI:https://doi.org/10.1016/j.nimb.2021.06.007· OSTI ID:1806258

Zirakparvar, N. Alex; Spano, Tyler L.; Miskowiec, Andrew; Smith, Julie B.; Hexel, Cole R.; Ambrogio, Michael; Kapsimalis, Roger

We investigate the sputtering and ionization process that takes place during secondary ion mass spectrometry (SIMS) analysis in order to develop a better understanding of the underlying controls on elemental and molecular oxide secondary ion yields. Using data from a suite of uranium compounds that were sputtered with an O- primary beam on a NanoSIMS 50L, our goal is to understand whether a compound’s intrinsic properties, or processes operating at the sputtering site, exert the greatest influence over the relative abundances of uranium elemental and molecular oxide secondary ions observed during an analysis. While the observed ²³⁸U/²³⁸U¹⁶O and ²³⁸U/²³⁸U¹⁶O₂ of the various compounds exhibit considerable overlap, there are relationships between the weighted mean ²³⁸U/²³⁸U¹⁶O and ²³⁸U/²³⁸U¹⁶O₂ ratios for the various compounds and their enthalpies of formation. This reinforces the existing theory that the nature of the material being sputtered can influence relative ion yields (e.g. the SIMS matrix effect), but we also document significant evidence for the influence of processes operating at the sputtering site as a major factor. The existence of a strong relationship between the relative uranium molecular oxide production rate and the mass fractionation regimes taking place within an analysis, as well as the existence of sudden shifts in molecular oxide production rates taking place within an analysis, provide further evidence for the importance of processes related to the sputtering and ionization dynamics as exerting the most control over observed ion yields. Evaluation of our data within the context of existing models for secondary ion production during SIMS analysis highlights the need for additional models that consider the competing influences of a sample’s chemical and/or structural form, reactions taking place at the sputtering site, as well as the ionization and ion extraction dynamics of the various elemental and molecular oxide species.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1806258
• Alternate ID(s): OSTI ID: 1810006
• Journal Information: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Journal Name: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Vol. 502 Journal Issue: C; ISSN 0168-583X
• Publisher: Elsevier
• Country of Publication: Netherlands
• Language: English

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