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