A LEED-AES study of the oxidation of cr(110) and Cr(100)

doi:10.1016/0039-6028(73)90061-7

Surface Science

Volume 40, Issue 1, October 1973, Pages 179-199

https://doi.org/10.1016/0039-6028(73)90061-7 Get rights and content

Abstract

The initial stages of the oxidation of (110) and (100) chromium surfaces have been studied using low energy electron diffraction and Auger electron spectroscopy. The low energy Auger electron peaks were tentatively explained in terms of different chemical states. Thus, the clean chromium surface, the surface covered by chemisorbed oxygen and the chromium oxide surface could be associated with the occurrence of different peaks. The intermediate oxygen chemisorption structures observed at oxidation, have been characterized with respect to symmetry and accurate unit cell dimensions. Lattice parameters were found to range from those of the substrate chromium metal to those of chromium sesquioxide. On the (110) face, the lattice parameter change was observed to be largest in the [11̄0] direction. The observations are in fair agreement with current concepts of misfitting crystalline surface layers.

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The obtained data indicate that most of the oxygen is simply adsorbed. Further detailed information on the initial stages of oxidation of Cr, proposed as models, can be found in [10,13,16–18]. In contrast to the above studied metals, the spectra obtained from a Zn surface revealed no remarkable oxygen uptake, as shown in the relative concentration plot in Fig. 3d).
Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a common procedure for thorough material investigations, where clean surfaces free of any contamination are essential. Hence, surface analytic studies are mostly performed under ultra-high vacuum (UHV) conditions, but the cleanness of such UHV environments is usually overrated. Consequently, the current study highlights the in principle known impact of the residual gas on metal surfaces (Fe, Mg, Al, Cr and Zn) for various surface analytics methods, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The investigations with modern, state-of-the-art equipment showed different behaviors for the metal surfaces in UHV during acquisition: (i) no impact for Zn, even after long time, (ii) solely adsorption of oxygen for Fe, slight and slow changes for Cr and (iii) adsorption accompanied by oxide formation for Al and Mg. The efficiency of different counter measures was tested and the acquired knowledge was finally used for ZnMgAl coated steel to obtain accurate depth profiles, which exhibited before serious artifacts when data acquisition was performed in an inconsiderate way.
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At low r/p values, the overexposure to oxygen causes an excessive substrate oxidation, resulting in a poorly ordered MgO film, while high r/p values induce the development of under-stoichiometric MgO films (see Fig. 10). Epitaxial Cr2O3 films have been stabilized on the Cr(011) surface [173–178]. Oxygen exposure in UHV conditions performed with the substrate held at relatively high temperatures (603 K) induces the layer-by-layer growth of Cr2O3, without any interface roughening [174].
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Citation Excerpt :
We cannot exclude that, as a consequence of the post-annealing treatments at 200 °C an alloyed Ni–Fe phase is formed in proximity of the interface underneath the oxidized layer. Before presenting our results on the oxidation of Cr ultra-thin films deposited on Fe it is useful to summarize the results obtained by Ekelund et al. in the oxidation of (110) and (100) chromium surfaces [42]. According to their investigations, two different spectroscopic features in the low energy Auger spectra are associated to Cr oxidation.
The effects of oxygen exposure on ultrathin films of Ni and Cr deposited on Fe(001) are studied by means of low energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy.
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A LEED-AES study of the oxidation of cr(110) and Cr(100)

Abstract

Surface Sci.

Surface Sci.

J. Colloid Interface Sci.

Phys. Letters

Vacuum

Surface Sci.

Surface Sci.

Surface Sci.

Surface Sci.

Acta Met.

J. Vacuum Sci. Technol.

Rev. Sci. Instr.