Double matrix effect in Low Energy Ion Scattering from La surfaces

Andrey A. Zameshin* (Corresponding Author), Andrey E. Yakshin, Jacobus M. Sturm, Hidde H. Brongerma, Fred Bijkerk

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

3 Citations (Scopus)
17 Downloads (Pure)

Abstract

Low Energy Ion Scattering (LEIS) has been performed on several lanthanum-based surfaces. Strong subsurface matrix effects – dependence of surface scattered He+ ion yield on the composition of subsurface layer – have been observed. The ion yield of He+ scattered by La differed by a factor of up to 2.5 for different surfaces, while only the La peak was visible in the spectra. To study these effects and enable surface quantification, He+ ion yields have been measured in a range of incident He+ energies from 1000 to 7500 eV for LaB6, La2O3, oxidized La and pure La surfaces. The investigation showed that as many as two simultaneous matrix effects are present, each one driven by a separate charge exchange mechanism. The first one is a resonant neutralization from the conduction band of La to an excited state of the He+ ion. It depends on the work function of the surface, which is lowered significantly when La interacts with O or B. The second mechanism is quasiresonant charge transfer between bound La levels and He 1s, which creates characteristic oscillations in the energy dependence of ion yields. The exact structure of the oscillations depends on small changes in binding energies of interacting La levels. This is the first time quasiresonant charge transfer is proven to be present in La. It is likely that La 5p orbitals participate in this resonance, which can be the first clear observation of a resonance between p and s orbitals in LEIS. This type of resonance was previously believed to be absent because of strong damping. We also demonstrated that despite the complex matrix effect precise measurements over a wide energy range allow quantification of the atomic composition of La-based surfaces.

Original languageEnglish
Pages (from-to)570-579
Number of pages10
JournalApplied surface science
Volume440
Early online date2 Feb 2018
DOIs
Publication statusPublished - 15 May 2018

Fingerprint

Scattering
Ions
Charge transfer
Lanthanum
Conduction bands
Binding energy
Chemical analysis
Excited states
Damping

Keywords

  • Lanthanum
  • LEIS
  • Low Energy Ion Scattering
  • Matrix effect
  • Oscillatory ion yield
  • Work function

Cite this

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title = "Double matrix effect in Low Energy Ion Scattering from La surfaces",
abstract = "Low Energy Ion Scattering (LEIS) has been performed on several lanthanum-based surfaces. Strong subsurface matrix effects – dependence of surface scattered He+ ion yield on the composition of subsurface layer – have been observed. The ion yield of He+ scattered by La differed by a factor of up to 2.5 for different surfaces, while only the La peak was visible in the spectra. To study these effects and enable surface quantification, He+ ion yields have been measured in a range of incident He+ energies from 1000 to 7500 eV for LaB6, La2O3, oxidized La and pure La surfaces. The investigation showed that as many as two simultaneous matrix effects are present, each one driven by a separate charge exchange mechanism. The first one is a resonant neutralization from the conduction band of La to an excited state of the He+ ion. It depends on the work function of the surface, which is lowered significantly when La interacts with O or B. The second mechanism is quasiresonant charge transfer between bound La levels and He 1s, which creates characteristic oscillations in the energy dependence of ion yields. The exact structure of the oscillations depends on small changes in binding energies of interacting La levels. This is the first time quasiresonant charge transfer is proven to be present in La. It is likely that La 5p orbitals participate in this resonance, which can be the first clear observation of a resonance between p and s orbitals in LEIS. This type of resonance was previously believed to be absent because of strong damping. We also demonstrated that despite the complex matrix effect precise measurements over a wide energy range allow quantification of the atomic composition of La-based surfaces.",
keywords = "Lanthanum, LEIS, Low Energy Ion Scattering, Matrix effect, Oscillatory ion yield, Work function",
author = "Zameshin, {Andrey A.} and Yakshin, {Andrey E.} and Sturm, {Jacobus M.} and Brongerma, {Hidde H.} and Fred Bijkerk",
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day = "15",
doi = "10.1016/j.apsusc.2018.01.174",
language = "English",
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Double matrix effect in Low Energy Ion Scattering from La surfaces. / Zameshin, Andrey A. (Corresponding Author); Yakshin, Andrey E.; Sturm, Jacobus M.; Brongerma, Hidde H.; Bijkerk, Fred.

In: Applied surface science, Vol. 440, 15.05.2018, p. 570-579.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Double matrix effect in Low Energy Ion Scattering from La surfaces

AU - Zameshin, Andrey A.

AU - Yakshin, Andrey E.

AU - Sturm, Jacobus M.

AU - Brongerma, Hidde H.

AU - Bijkerk, Fred

PY - 2018/5/15

Y1 - 2018/5/15

N2 - Low Energy Ion Scattering (LEIS) has been performed on several lanthanum-based surfaces. Strong subsurface matrix effects – dependence of surface scattered He+ ion yield on the composition of subsurface layer – have been observed. The ion yield of He+ scattered by La differed by a factor of up to 2.5 for different surfaces, while only the La peak was visible in the spectra. To study these effects and enable surface quantification, He+ ion yields have been measured in a range of incident He+ energies from 1000 to 7500 eV for LaB6, La2O3, oxidized La and pure La surfaces. The investigation showed that as many as two simultaneous matrix effects are present, each one driven by a separate charge exchange mechanism. The first one is a resonant neutralization from the conduction band of La to an excited state of the He+ ion. It depends on the work function of the surface, which is lowered significantly when La interacts with O or B. The second mechanism is quasiresonant charge transfer between bound La levels and He 1s, which creates characteristic oscillations in the energy dependence of ion yields. The exact structure of the oscillations depends on small changes in binding energies of interacting La levels. This is the first time quasiresonant charge transfer is proven to be present in La. It is likely that La 5p orbitals participate in this resonance, which can be the first clear observation of a resonance between p and s orbitals in LEIS. This type of resonance was previously believed to be absent because of strong damping. We also demonstrated that despite the complex matrix effect precise measurements over a wide energy range allow quantification of the atomic composition of La-based surfaces.

AB - Low Energy Ion Scattering (LEIS) has been performed on several lanthanum-based surfaces. Strong subsurface matrix effects – dependence of surface scattered He+ ion yield on the composition of subsurface layer – have been observed. The ion yield of He+ scattered by La differed by a factor of up to 2.5 for different surfaces, while only the La peak was visible in the spectra. To study these effects and enable surface quantification, He+ ion yields have been measured in a range of incident He+ energies from 1000 to 7500 eV for LaB6, La2O3, oxidized La and pure La surfaces. The investigation showed that as many as two simultaneous matrix effects are present, each one driven by a separate charge exchange mechanism. The first one is a resonant neutralization from the conduction band of La to an excited state of the He+ ion. It depends on the work function of the surface, which is lowered significantly when La interacts with O or B. The second mechanism is quasiresonant charge transfer between bound La levels and He 1s, which creates characteristic oscillations in the energy dependence of ion yields. The exact structure of the oscillations depends on small changes in binding energies of interacting La levels. This is the first time quasiresonant charge transfer is proven to be present in La. It is likely that La 5p orbitals participate in this resonance, which can be the first clear observation of a resonance between p and s orbitals in LEIS. This type of resonance was previously believed to be absent because of strong damping. We also demonstrated that despite the complex matrix effect precise measurements over a wide energy range allow quantification of the atomic composition of La-based surfaces.

KW - Lanthanum

KW - LEIS

KW - Low Energy Ion Scattering

KW - Matrix effect

KW - Oscillatory ion yield

KW - Work function

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U2 - 10.1016/j.apsusc.2018.01.174

DO - 10.1016/j.apsusc.2018.01.174

M3 - Article

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