Influence of compaction and surface roughness on low‐energy ion scattering signals

Jansen, Wilma; Knoester, Arie; Maas, A. J. H.; Schmit, Pauline; Kytökivi, Arla; Gon, A. W. Denier van der; Brongersma, Hidde H.

doi:10.1002/sia.1921

Cited by 22 publications

(16 citation statements)

References 22 publications

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“…On the GaAs(111) A substrate, the film 296A was found to grow without rotational growth twins evident, while for growth on GaAs(111) B , film 296B showed twinned domains where the triangular features on the surface rotate 180° relative to each other. Although surface roughness decreases the absolute signal intensity in LEIS, it does not influence the ratios of signal intensities . The surfaces are sufficiently flat that gross surface roughness should not have affected any of the measurements reported here.…”

Section: Resultsmentioning

confidence: 61%

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se₂ for photovoltaic applications

Téllez

Druce

Hall

et al. 2014

Progress in Photovoltaics

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Cu(In,Ga)Se 2 (CIGS) single-crystal epitaxial films have been analyzed by low energy ion scattering, which is sensitive to exactly the outermost surface atomic layer, to determine the surface chemistry as a function of preparation conditions. The samples were grown by a hybrid sputtering and evaporation method on cation (A) or anion (B) terminated (111) GaAs substrates and had smooth surfaces. The samples were exposed to excited atomic oxygen or hydrogen beams or were sputtered with 500 eV Ar + ions. Atomic O* treatment resulted in an otherwise clean, oxidized surface including all film constituents. Atomic H* resulted in strong enhancement of the surface Ga population, probably due to a preexisting Ga native oxide in the outermost atomic layer. Sputtering produced a clean surface that was closest to the bulk composition of the film as measured by energy-dispersive spectroscopy.

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Section: Resultsmentioning

confidence: 61%

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se₂ for photovoltaic applications

Téllez

Druce

Hall

et al. 2014

Progress in Photovoltaics

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“…The signal reduction for the powder can thus be explained by its roughness (and not to a different composition). This signal reduction is typical for a powder 16 …”

Section: Resultsmentioning

confidence: 75%

Quantitative analysis of calcium and fluorine by high‐sensitivity low‐energy ion scattering: Calcium fluoride

Průša

Bábík

Šikola

et al. 2020

Surface & Interface Analysis

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Low-energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well-defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF 2 as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF 2 is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF 2 can be used as reference, its atomic surface concentrations have to be determined. Here, 3-keV He + scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. Highpurity CaF 2 is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF 2 (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu.

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“…From the comparison of the LEIS intensities of the samples with those of reference metal surfaces recorded under identical conditions, the average sizes of the alloy nanoparticles can be assessed on the basis of a spherical particle model . The required specific support surface areas were derived from a value of 800 m 2 g −1 for the pure Ketjen Black support.…”

Section: Resultsmentioning

confidence: 99%

Chemical Leaching of Pt–Cu/C Catalysts for Electrochemical Oxygen Reduction: Activity, Particle Structure, and Relation to Electrochemical Leaching

et al. 2016

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Carbon‐supported Pt–Cu alloy nanoparticles (Cu/Pt=2.6 on average) were obtained by a liquid precursor impregnation–reduction technique, with alloying in dilute hydrogen at 800 °C. They were subjected to leaching (chemical—CL: 1 m H2SO4, 80 °C for 36 h, electrochemical—EL: 200 times potential cycling between 0.05 and 1.2 V in 0.1 m HClO4) to study the influence of leaching on their activity in the oxygen reduction reaction (ORR) and on particle structure, in particular, for the chemical route that provided sufficient material for the characterization techniques employed (X‐ray diffraction, X‐ray absorption spectroscopy, X‐ray photoelectron spectroscopy, low‐energy ion scattering). CL resulted in core–shell‐structured nanoparticles, in which an external monolayer of pure Pt covered an alloy core significantly depleted in Cu. Cu/Pt ratios in the cores were distributed around Cu/Pt=0.4–1, which differs from particle architectures described in the literature as a result of EL. The alloy superstructure initially present was destroyed. A minority of pure Pt particles, probably very small in size, coexisted with the alloy particles. The specific ORR activity of these leached nanoparticles was twice that of the original Pt–Cu alloy particles (264 vs. 140 μA cm−2 Pt). Electrochemical leaching applied to the initial particles or to the chemically dealloyed ones also resulted in activation (direct EL −175 μA cm−2 Pt, EL after CL −315 μA cm−2 Pt). Particles with a Cu‐depleted alloy core (EL after CL) provided higher activity after EL.

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Influence of compaction and surface roughness on low‐energy ion scattering signals

Abstract: The results on the oxidized silicon confirm the small influence of surface roughness for silica particles, whereas measurements on the more closely packed metallic gallium and gold surfaces indicate a significant surface roughness effect.

Cited by 22 publications

References 22 publications

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se₂ for photovoltaic applications

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se₂ for photovoltaic applications

Quantitative analysis of calcium and fluorine by high‐sensitivity low‐energy ion scattering: Calcium fluoride

Chemical Leaching of Pt–Cu/C Catalysts for Electrochemical Oxygen Reduction: Activity, Particle Structure, and Relation to Electrochemical Leaching

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Influence of compaction and surface roughness on low‐energy ion scattering signals

Abstract: The results on the oxidized silicon confirm the small influence of surface roughness for silica particles, whereas measurements on the more closely packed metallic gallium and gold surfaces indicate a significant surface roughness effect.

Cited by 22 publications

References 22 publications

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se2 for photovoltaic applications

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se2 for photovoltaic applications

Quantitative analysis of calcium and fluorine by high‐sensitivity low‐energy ion scattering: Calcium fluoride

Chemical Leaching of Pt–Cu/C Catalysts for Electrochemical Oxygen Reduction: Activity, Particle Structure, and Relation to Electrochemical Leaching

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Product

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Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se₂ for photovoltaic applications

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se₂ for photovoltaic applications