Determination of 16O and 18O sensitivity factors and charge-exchange processes in low-energy ion scattering

Abstract

Quantitative analysis in low-energy ion scattering (LEIS) requires an understanding of the charge-exchange processes to estimate the elemental sensitivity factors. In this work, the neutralization of He+ scattered by 18O-exchanged silica at energies between 0.6 and 7 keV was studied. The process is dominated by Auger neutralization for Ei < 0.8 keV. An additional mechanism starts above the reionization threshold. This collision-induced neutralization becomes the dominant mechanism for Ei > 2 keV. The ion fractions P+ were determined for Si and O using the characteristic velocity method to quantify the surface density. The 18O/16O sensitivity ratio indicates an 18% higher sensitivity for the heavier O isotope.

The effect of sub-surface strontium depletion on oxygen diffusion in La0.6Sr0.4Co0.2Fe0.8O3−δ

“…It should be noted that LEIS sensitivity for 18 O is approximately 18% greater than 16 O and was scaled appropriately. 40 Secondary ion mass spectrometry. SIMS was performed on the exchanged sample in order to measure the oxygen tracer diffusion prole.…”

Surface Compositions of Oxide Supported Bimetallic Catalysts: A Compared Study by High‐Sensitivity Low Energy Ion Scattering Spectroscopy and X‐Ray Photoemission Spectroscopy

“…The surface coverage of each element is proportional to the measured intensity (Figure B). LEIS is one of the most powerful techniques to measure the topmost surface composition, as well as the growth of surface thin films (Figure ) . However, the conventional LEIS is limited to a smooth surface .…”

“…Thus, little progress has been made about the top surface composition for a supported catalyst. Recently developed high‐sensitivity LEIS (HS‐LEIS) (IONTOF Qtac100, Figure C) can achieve about 3000 times higher sensitivity than the conventional one, which offers possibility to measure the top surface composition for a supported catalyst . With a homemade pretreatment reaction cell, the sample can be treated under realistic catalytic reaction conditions and transferred into the analysis chamber under vacuum .…”

New perspectives in the surface analysis of energy materials by combined time-of-flight secondary ion mass spectrometry (ToF-SIMS) and high sensitivity low-energy ion scattering (HS-LEIS)

“…In this sense, LEIS is the only analysis technique capable of providing precise information about the 18 O concentration at the gas-solid interface at the rst atomic layer, which is the active surface where exchange takes place. 5 Furthermore, the elemental sensitivity factors and the survival probability for 4 He + scattering by 18 O and 16 O have been recently reported, 24 and hence, the quantitative analysis of the oxygen surface coverage can be reliably performed.…”

“…Therefore, quantitative LEIS analysis is considered to be straightforward for oxidic surfaces, 22,23 provided that a single neutralisation mechanism takes place under the chosen analytical conditions. 24 Further discussion about some rare exceptions where matrix effects are present for quantitative LEIS analysis can be found in the study by Brongersma et al 18 Table 1 summarizes the analytical performance of the two techniques.…”