The effect of glow discharge sputtering on the analysis of metal oxide films

Julien Malherbe (1) , Hervé Martinez (1) , B. Fernandez , Christophe Pécheyran (1) , Olivier François Xavier Donard (1)

1 IPREM - Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux

The potential of radiofrequency glow discharge optical emission spectrometry (rf-GD-OES) for the quantification and the solid-state speciation of metal oxide films has been investigated in this work. Two types of oxide coatings, an iron oxide film deposited on silicon and a chromate conversion coating (CCC), were studied at 700 Pa of pressure and 30 W of forward power. The metal to oxygen ratios in the quantitative depth profiles (Fe/O and Cr/O, respectively) were used to evaluate the oxidation states of iron and chromium in the oxide films, demonstrating the capability of GD-OES technique for depth-resolved solid-state speciation. Furthermore, the effect of glow discharge sputtering on the samples surface in terms of modifications in the surface morphology and species transformations, were investigated by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The iron and chromium oxidation states were carefully studied by XPS at the original samples surface and at the bottom of GD craters, and a systematic reduction of metal elements was observed after rf-GD-OES analysis. In the case of thin oxide films, preferential sputtering can be considered as a critical factor since oxygen atoms can be preferentially sputtered, leaving a metal-enriched surface and, therefore, promoting the reduction of metal elements. In the present study preferential sputtering was found to be sample dependent, changing the proportion of the metal reduction in the oxide film with its composition. Additionally, alternative sputter-depth-profiling techniques such as secondary ion mass spectrometry (SIMS), femtosecond laser ablation (fs-LA), and XPS ion gun were used for the analysis of the CCC in order to evaluate the reduction of Cr6+ to Cr3+ depending on the sputtering mechanism. © 2008 Elsevier B.V. All rights reserved.

Mots clés: Ablation; Atomic force microscopy; Atomic force microscopy (AFM); Atomic physics; Atomic spectroscopy; Atoms; Chromate coatings; Chromates; chromium; Depth profiling; Electric discharges; Electron spectroscopy; Emission spectroscopy; Fourier transforms; Glow discharges; High performance liquid chromatography; In-depth profile analysis; Iron analysis; Iron oxides; Laser ablation; Light emission; Mass spectrometry; Metal analysis; Metallic compounds; Metals; Optical emission spectroscopy; Optical microscopy; oxidation; Oxide films; Oxygen; Photoelectricity; Photoelectron Spectroscopy; Photoionization; Photons; Plasmas; Preferential sputtering; Protective coatings; Pulsed laser applications; Radiofrequency glow discharge optical emission spectrometry (rf-GD-OES); secondary ion mass spectrometry; Solid-state speciation; Spectrometers; Spectrometry; Spectrum analysis; Surface morphology; X ray analysis; X ray photoelectron spectroscopy; X-ray photoelectron spectroscopy (XPS)

Domaines: Chimie; Matériaux

Julien Malherbe, Hervé Martinez, B. Fernandez, Christophe Pécheyran, Olivier François Xavier Donard. The effect of glow discharge sputtering on the analysis of metal oxide films. Spectrochimica Acta Part B: Atomic Spectroscopy, 2009, 64 (2), pp.155--166. ⟨10.1016/j.sab.2008.11.009⟩. ⟨hal-01504344⟩