Glow Discharge Optical Emission Spectroscopy Depth Profiling Research Articles

Understanding early-stage oxidation mechanism of Crofer 22 APU solid oxide fuel cell steel interconnect using glow discharge optical emission spectroscopy and grazing incidence X-ray diffraction

Crofer 22 APU is used as metallic interconnects in stacking solid oxide fuel cells (SOFCs) operated at elevated temperatures (above 700 °C) owing to their excellent oxidation resistance. Understanding the protective layer formation in the initial oxidation stage would be useful for optimizing and designing protective coatings for extended life. Initial stage oxidation of Crofer 22 APU steel using surface analytical tools such as glow discharge optical emission spectroscopy (GD-OES), grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, and atomic force microscopy (AFM) are studied in the paper. An oxidation test on as-received Crofer 22 APU steel was carried out in a controlled atmosphere (0.01 Pa) in an in-situ high-temperature X-ray diffraction (XRD) stage at 950 °C. Normal XRD showed no indication of oxidation, while GIXRD revealed the formation of two-layer oxides: Top layer spinel MnCr2O4 and fine-grained inner layer Cr2O3, which was confirmed and quantified by GD-OES depth profiling. The Cr2O3 formed initially led to the formation of MnCr2O4 spinel during the initial stage. The rapid diffusion of Mn through the fine-grained Cr2O3 layer results in an increased growth rate of MnCr2O4 spinel on the top of the fine-grained Cr2O3 layer.

Detection of Li Deposition on Si/Graphite Anodes from Commercial Li-Ion Cells: A Post-Mortem GD-OES Depth Profiling Study

A new semi-quantitative method was developed to detect Li deposition on Si/graphite anodes. This method is based on Post-Mortem glow discharge optical emission spectroscopy (GD-OES) depth profiling. Based on the contents of Si, Li, and O in the GD-OES depth profiles, we define a corridor, in which the minimum amount of metallic Li on the anode is located. This method was applied to three types of commercial 18650 cells with Si/graphite anodes in the fresh state and with Li plating intentionally produced by cycling at low temperatures. Additional cells were cycling aged at 45 °C to 80% SOH. The main aging mechanisms at 45 °C were determined using differential voltage analysis (DVA), SEM, and half cell experiments. Subsequently, the cells aged at 45 °C were further cycled under the conditions that had led to Li deposition for the fresh cells. Furthermore, the anode coating thickness for 18 types of commercial Li-ion cells are correlated with the specific energy, while distinguishing between graphite anodes and Si/graphite anodes. Our extensive Post-Mortem study gives deep insights into the aging behavior of state-of-the-art Li-ion cells with Si/graphite anodes.

Determination of the Interface Roughness between Ni-Coated Layer and Cu Substrate by Glow Discharge Optical Emission Spectroscopy Depth Profiling

The depth profiles of Ni-coated copper substrates polished by different mesh size sandpapers were measured by the glow discharge optical emission spectroscopy (GDOES) depth profiling technique. The measured depth profiles were well fitted by the MRI-CRAS model developed recently on the basis of the Mixing-Roughness-Information depth (MRI) model and the CRAter-Simulation (CRAS) model, taking into account the pronounced crater effect upon GDOES depth profiling. The crater effect upon depth profiling was characterized quantitatively and the interface roughness values between the coated Ni layer and the Cu substrates were determined and compared with the ones measured by AFM.

Determination of Coated Substrate Roughness by Quantification of Measured Depth Profiles

The glow discharge optical emission spectroscopy (GDOES) depth profiles of zinc-coated copper substrates polished by different mesh size sandpapers are well fitted with the mixing-roughness-information (MRI) model. Based on the MRI fits, the copper substrate roughness parameters and the coating layer thickness values are extracted. Using the so-called 84% to 16% method, the depth resolution values of the measured GDOES depth profiles are obtained, thereby the respective roughness parameters are determined. The obtained zinc-coated copper substrate roughness values are correlated with the experimental measurements.

Study of the near-surface of hot- and cold-rolled AlMg0.5 aluminium alloy

Rolling is known to alter the surface properties of aluminium alloys and to introduce disturbed near-surface microcrystalline layers. The near-surfaces of mostly higher alloyed materials were investigated by various techniques, often combined with a study of their electrochemical behaviour. Cross-sectional transmission electron microscopy (TEM), after ion milling or ultramicrotomy, indicated the presence of disturbed layers characterized by a refined grain structure, rolled-in oxide particles and a fine distribution of intermetallics. Those rolled-in oxide particles reduce the total reflectance of rolled Al alloys. Furthermore, various depth profiling techniques, such as AES, XPS, SIMS and qualitative glow discharge optical emission spectroscopy (GD-OES) have been used to study the in-depth behaviour of specific elements of rolled Al alloys. Here, the surface and near-surface of AlMg0.5 (a commercially pure rolled Al alloy with addition of 0.5 wt.% Mg) after hot and cold rolling, and with and without additional annealing is studied with complementary analytical techniques. Focused ion beam thinning is introduced as a new method for preparing cross-sectional TEM specimens of Al surfaces. Analytical cross-sectional TEM is used to investigate the microstructure and composition. Measuring the total reflectance of progressively etched samples is used as an optical depth profiling method to derive the thickness of disturbed near-surface layers. Quantitative r.f. GD-OES depth profiling is introduced to study the in-depth behaviour of alloying elements, as well as the incorporation of impurity elements within the disturbed layer. The GD-OES depth profiles, total reflectance and cross-sectional TEM analyses are correlated with SEM/energy-dispersive x-ray observations in GD-OES craters. Copyright © 2005 John Wiley & Sons, Ltd.

Analysis of anodic films on Nb and NbNx by glow discharge optical emission spectroscopy

AbstractSputter‐deposited niobium layers containing nitrogen form anodic films with resultant capacitance and leakage current density little influenced by annealing up to 523 K. The nitrogen species incorporated into the anodic oxide films at the alloy/film interface are distributed in the inner 70–75% of the film thickness, with fine bubbles containing high‐pressure N2O gas being evident. Glow discharge optical emission spectroscopy (GDOES) analysis reveals their continued presence after annealing at 523 K. The insignificant changes in GDOES depth profiles also suggest that the formation of low‐valent oxide at the metal/film interface as a result of annealing is not responsible for the behaviour. For thermal treatments above 400 K, capacitances and leakage currents increase significantly for niobium, with nitrogen additions diminishing the effects. Such behaviour is suggested to arise from suppression of mechanical damage to films through the presence of highly pressurized gas in the inner part of the films. Copyright © 2003 John Wiley & Sons, Ltd.

Investigation of SiO2 layers by glow discharge optical emission spectroscopy including layer thickness determination by an optical interference effect

When analysing transparent layers on reflecting substrates, the effect of interference causes intensity oscillations of certain spectral lines in glow discharge optical emission spectroscopy (GD-OES). As well as the chemical information that can be obtained from GD-OES depth profiles, this effect provides additional information for the determination either of layer thickness or of refractive index. Chemical characterisation and layer thickness determination were carried out on SiO2 layers deposited by different methods using GD-OES. In some cases the calculated layer thickness was compared with data gained by ellipsometry. The results of layer thickness determination using the emission lines of Si at 288 nm and Ar at 416 nm, obtained at a homogeneous thermally oxidised silicon wafer, show the present state of the art of accuracy and precision of this analytical method.

GDOES depth profiling analysis and cross-sectional transmission electron microscopy of a hard disk

Through the analysis of a commercial hard disk, it is demonstrated that glow discharge optical emission spectroscopy (GDOES) is a powerful technique for depth profiling analysis of surfaces coated with multilayers of widely differing thicknesses, ranging from a few tens of nanometres to several tens of microns. This arises from its high depth resolution, resulting from highly uniform sputtering, and its wide thickness range, resulting from its high sputtering rate. The depth profile obtained agreed precisely with the layered structure of the disk revealed directly by cross-sectional transmission electron microscopy. Copyright © 2000 John Wiley & Sons, Ltd.

Interference Phenomena at Transparent Layers in Glow Discharge Optical Emission Spectrometry

At the performance of depth profiling by glow discharge optical emission spectroscopy (GD-OES) the intensities of optical emission lines of sample and sputter gas elements are measured in dependence on the time of sputtering. Radio-frequency (rf) sputtering extended the field of application to nonconducting samples including transparent layers. For transparent coatings in the thickness range up to some micrometers, oscillations of measured intensities were observed. This behavior is explained by a thin-film interference effect and discussed for three different materials, i.e., SiO2, TiO2, and BaTiO3. As a result, a new procedure for the determination of either layer thickness or refractive index from GD-OES depth profiles is presented. This effect has to be considered for quantitative GD-OES analysis as well.

Influence of surface roughness on the depth resolution of GDOES depth profiling analysis

Radio-frequency-powered glow discharge optical emission spectroscopy (GDOES) is an extremely powerful and reliable technique for depth profiling analysis of thin, insulating barrier anodic films formed on aluminium. It allows ready and rapid analysis of the films, with depth resolution and sensitivity comparable with, or better than, those of secondary ion mass spectrometry depth profiling. However, for successful application of the technique, surfaces of specimens should be microscopically flat; surface roughness of dimensions similar to the thickness of the films can lead to almost total degradation of the depth profiles. Copyright © 1999 John Wiley & Sons, Ltd.

Multilayer reference coatings for depth profile standards

Depth profiles of layer systems consisting of different film materials and having different thicknesses are of great practical importance. Multilayer reference coatings of conducting (Ti/Al) and non-conducting (SiO 2/Si 3N 4) material are analyzed with Auger electron spectroscopy (AES) and glow discharge optical emission spectroscopy (GDOES) depth profiling. Deposition techniques, physical vapor deposition for Ti/Al layers and plasma-enhanced chemical vapor deposition for SiO 2/Si 3N 4 layers, as well as measurement and testing procedures for the determination of layer thickness such as optical and mechanical stylus and spectroscopie ellipsometry are discussed. GDOES depth profiles in direct current (d.c.) and radio frequency (r.f.) mode are related to measurements of crater profiles and compared with line scans and depth profiles performed by AES. It is shown that such multilayer reference systems are appropriate for calibration of depth profiles, i.e. the definition and the evaluation of the depth resolution at the interface, the determination of sputter rates both for d.c.- and r.f.-GDOES and AES, the optimization of the conditions of analysis, and the quantification of analysis itself.

High-temperature oxidation of iron covered by electroless Ni?P coating: A GDOS depth profiling study

Steel samples coated by electroless nickel were annealed in air. Oxide growth kinetics and iron diffusion through the structure were investigated by glow discharge optical emission spectroscopy (GDOS) depth profiling. Protection against high-temperature oxidation was found to be given mostly by the austenitic interdiffusion layer formed at the interface between the substrate and the Ni-P film during annealing of the sample, which acts as a diffusion barrier for diffusion of iron to the surface.