Resolving the depth coordinate in photoelectron spectroscopy – Comparison of excitation energy variation vs. angular-resolved XPS for the analysis of a self-assembled monolayer model system

Merzlikin, Sergiy Vasil ́ović; Tolkachev, N. N.; Strunskus, Thomas; Witte, Gregor; Głogowski, T.; Wöll, Christof; Grünert, Wolfgang

doi:10.1016/j.susc.2007.12.005

Cited by 65 publications

(57 citation statements)

References 24 publications

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“…The fact that even standard XPS equipment reaches surface sensitivities as low as 1 nm makes XPS into a powerful tool for core-shell characterization, especially for particles with shell thicknesses larger than 1 nm [4,12,13,45]. Despite the high surface sensitivity, a sampling depth comparable to the outermost atomic layer still cannot be reached [34].…”

Section: X-ray Spectroscopiesmentioning

confidence: 99%

How to Determine the Core-Shell Nature in Bimetallic Catalyst Particles?

Westsson

Koper

2014

Catalysts

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Nanometer-sized materials have significantly different chemical and physical properties compared to bulk material. However, these properties do not only depend on the elemental composition but also on the structure, shape, size and arrangement. Hence, it is not only of great importance to develop synthesis routes that enable control over the final structure but also characterization strategies that verify the exact nature of the nanoparticles obtained. Here, we consider the verification of contemporary synthesis strategies for the preparation of bimetallic core-shell particles in particular in relation to potential particle structures, such as partial absence of core, alloying and raspberry-like surface. It is discussed what properties must be investigated in order to fully confirm a covering, pinhole free shell and which characterization techniques can provide such information. Not uncommonly, characterization strategies of core-shell particles rely heavily on visual imaging like transmission electron microscopy. The strengths and weaknesses of various techniques based on scattering, diffraction, transmission and absorption for investigating core-shell particles are discussed and, in particular, cases where structural ambiguities still remain will be highlighted. Our main conclusion is that for particles with extremely thin or mono-layered shells-i.e., structures outside the limitation of most imaging techniques-other strategies, not involving spectroscopy or imaging, are to be employed. We will provide a specific example of Fe-Pt core-shell particles prepared in bicontinuous microemulsion and point out the difficulties that arise in the characterization process of such particles. OPEN ACCESSCatalysts 2014, 4 376

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Section: X-ray Spectroscopiesmentioning

confidence: 99%

How to Determine the Core-Shell Nature in Bimetallic Catalyst Particles?

Westsson

Koper

2014

Catalysts

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“…an overlayer/substrate sample, the influence may be rather strong, and the analysis may erroneously be considered to be unreliable. 37 The problem is easily illustrated in Eqs. (9) - (11), where the signal intensities depend exponentially on the emission angle, a, which is the local emission angle.…”

Section: ·2 Photoelectron Intensities From Flat Surfacesmentioning

confidence: 99%

Electron Spectroscopy of Corrugated Solid Surfaces

Zemek

2010

ANAL. SCI.

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This paper reviews work done of the influence of non-ideal surface topography on electron spectral intensities of surface-sensitive electron spectroscopic methods: primarily X-ray induced photoelectron spectroscopy (XPS) and concise Auger electron spectroscopy (AES), electron energy loss spectroscopy in the reflection mode (REELS), and elastic peak electron spectroscopy (EPES). Several attempts to solve the problem are mentioned, where (i) the effect of surface roughness is corrected using a single parameter, (ii) computer simulations based on a model of surface roughness composed of regular geometrical units are used for electron spectral intensity calculations, and finally, (iii) a semi-empirical method based on careful surface mapping of analyzed sample by atomic force microscopy (AFM) is discussed in greater detail. The first approach was found to be rather simple to properly include any complex surface topography. The second technique can help us to understand surface topography related phenomena. The latter method, suitable for arbitrary rough solid surfaces covered by conformal overlayer(s), can be incorporated in current quantitative procedures valid for ideally flat surfaces.

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“…However, the degree of surface smoothness for a sample is very important for TOA analysis, as reported by Merzlikin et al [8]. Unfortunately, many samples have bumps and dips on their surfaces, which makes TOA analysis difficult.…”

Section: Introductionmentioning

confidence: 98%