Characterization of chemical information and morphology for in‐depth oxide layers in decarburized electrical steel with glow discharge sputtering

A combination of scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy with a sampling method by glow discharge sputtering was successfully employed to characterize the chemical information and microscopic features of oxide layers formed during decarburization annealing of electrical steel in the depth direction at high resolution. The discontinuous surface oxides consisted of SiO₂, (Fe,Mn)SiO₃/(Fe,Mn)₂SiO₄, and FeO. SiO₂ embedded in the (Fe,Mn)₂SiO₄ at the surface may be developed by the preferential nucleation and growth kinetics. The discrete or often relatively spherical oxides of internal oxidation by the energetically favorable surface effect were identified as a mixture of SiO₂ and (Fe,Mn)₂SiO₄ at a depth of ~0.5 µm from the surface. The oxides of networks and small particles at a depth greater than ~1 µm were solely silica, of which the morphologies were possibly caused by the enhanced diffusion of oxygen atoms and Si atoms at grain boundaries or sub‐grain boundaries. The equilibrium and kinetic considerations served by theoretical calculations were introduced to understand the formation and behavior of the observed in‐depth oxidation. Copyright © 2013 John Wiley & Sons, Ltd.     

SIMS depth profiling of ‘frozen’ samples: in search of ultimate depth resolution regime

We have performed secondary ion mass spectrometry depth profiling analysis of III–V based hetero‐structures at different target temperatures and found that both the surface segregation and surface roughness caused by ion sputtering can be radically reduced if the sample temperature is lowered to ?150 °C. The depth profiling of ‘frozen’ samples can be a good alternative to sample rotation and oxygen flooding used for ultra‐low‐energy depth profiling of compound semiconductors. Copyright © 2016 John Wiley & Sons, Ltd.     

辉光放电光谱法在深度分析上的应用现状

本文简单地介绍了辉光放电光谱法（GD-OES）的基本原理。分别对深度分析的定量方式、放电方式、应用领域和相关标准进行了详细地阐述。重点描述了商品化仪器中使用的SIMR深度分析定量方法。分别对三种放电方式（如直流、射频和脉冲）在深度分析中的特点进行了介绍。综述了GD-OES在金属镀层、复杂涂镀层、纳米级薄膜和样品制备领域的具体应用。最后,介绍了GD-OES在深度分析方面的标准     

Measuring metal substrate roughness with glow discharge optical emission spectrometry

Although there are many methods to evaluate metal surface roughness, it is difficult to detect the substrate roughness of coated samples. Depth profile analysis (DPA) is proposed as a new method for the substrate roughness measurement, and glow discharge optical emission spectrometry (GDOES) becomes a candidate in substrate roughness measuring instruments. With this method, the typical roughness parameters R_a (arithmetic mean of the absolute deviation values of the roughness profile) and R_y (maximum value of consecutive peak and valley heights of the roughness profile along the sampling length) can be easily obtained. The principle of this method is discussed and the formulasof the principle are deducted in this paper. Electrodeposited zinc coating on copper substrate specimens is used as an example to explain the measuring process. Copyright © 2007 John Wiley & Sons, Ltd.     

SIMS depth profiling of semiconductor interfaces: Experimental study of depth resolution function

Reconstruction of original element distribution at semiconductor interfaces using experimental SIMS profiles encounters considerable difficulties because of the matrix effect, sputtering rate change at the interface, and also a sputtering‐induced broadening of original distributions. We performed a detailed depth profiling analysis of the Al step‐function distribution in GaAs/Al_xGa_1?xAs heterostructures by using Cs⁺ primary ion beam sputtering and CsM⁺ cluster ion monitoring (where M is the element of interest) to suppress the matrix effect. The experimental Depth Resolution Function (DRF) was obtained by differentiation of the Al step‐function profile and compared with the ‘reference’ DRF found from depth profiling of an Al delta layer. The difference between two experimental DRFs was explained by the sputtering rate change during the interface profiling. We experimentally studied the sputtering rate dependence on the Al_xGa_1?xAs layer composition and applied it for a reconstruction of the DRF found by differentiating the Al step‐function distribution: the ‘reconstructed’ and ‘reference’ DRFs were found to be in good agreement. This confirmed the correctness of the treatment elaborated. Copyright © 2010 John Wiley & Sons, Ltd.     

A statistical approach to delta layer depth profiling

We present a simple statistical model describing the removal and relocation of material during a sputter depth profiling experiment. All input parameters are determined from low‐fluence molecular dynamics simulations, making the model de facto parameter free. The model can be used to extrapolate data from the molecular dynamics simulations to projectile fluences relevant to sputter depth profiling experiments. As a result, the erosion of the surface is calculated in terms of fluence‐dependent filling factors of different sample layers. Using input data determined for the 20‐keV C₆₀ cluster bombardment of silicon, it is found that a steady‐state erosion profile is reached after removal of approximately 20 monolayer equivalents of material. Plotting the contribution of particles from a specific layer to the instantaneous sputtered flux, one can directly determine the delta layer response function predicted from such a model. It is shown that this function can be parameterized by the semiempirical Dowsett response function, and the resulting fitting parameters are compared with published depth profile data. The model is then used to study the role of different processes influencing the observed depth resolution. We find that the statistical nature of the sputtering process suffices to explain many features of experimentally measured delta layer depth profiles. Copyright © 2012 John Wiley & Sons, Ltd.     

A new approach to express ToF SIMS depth profiling

We propose a new approach to express SIMS depth profiling on a TOF.SIMS‐5 time‐of‐flight mass spectrometer. The approach is based on the instrument capability to independently perform raster scans of sputter and probe ion beams. The probed area can be much smaller than the diameter of a sputter ion beam, like in the AES depth profiling method. This circumstance alleviates limitations on the sputter beam–raster size relation, which are critical in other types of SIMS, and enables analysis on a curved‐bottomed sputter crater. By considerably reducing the raster size, it is possible to increase the depth profiling speed by an order of magnitude without radically degrading the depth resolution. A technique is proposed for successive improvement of depth resolution through profile recovery with account for the developing curvature of the sputtered crater bottom in the probed area. Experimental study of the crater bottom form resulted in implementing a method to include contribution of the instrumental artifacts in a nonstationary depth resolution function within the Hofmann's mixing–roughness–information depth model. The real‐structure experiment has shown that the analysis technique combining reduction of a raster size with a successive nonstationary recovery ensures high speed of profiling at ~100 µm/h while maintaining the depth resolution of about 30 nm at a 5 µm depth. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of nitrogen-influenced surface near zones of ferrous materials by glow discharge spectroscopy (GDOS)

Glow discharge spectroscopy (GDOS) will be shown to be a quick, informative and simple method for quantitative depth profile analysis of elements of nitrided layers well suited for their quality control. By systematic variation of all glow discharge determining parameters it is possible to get an excellent depth resolution in the order of sub-m corresponding to a comparatively large analytical activated area (50 mm²). In this paper the behaviour of a number of important parameters related to sputtering of the activated area will be discussed. Some quantitative GDOS depth profiles of carbon and nitrogen of pure iron samples nitrided by different procedures will be shown as examples for application.     

Quantitative determination of carbon concentration profiles by GD‐OES for the study of decarburization in low‐carbon steels

In this study, the quantification of decarburization induced during the annealing process for the fabrication of electrical steels was carried out using glow discharge optical emission spectroscopy (GD‐OES). Different calibration methods, based on external and internal standard references, were examined to optimize the quantification of carbon concentration. Accurate calibration curves for carbon at low concentration ranges were achieved by the use of carbon intensity calibrated by the internal reference, i.e. iron intensity line. This methodology was found to be beneficial for long GD‐OES measurements, providing a better correction over changes in the overall emission intensity with the sputter time. The good depth resolution obtained by the GD‐OES technique enabled the identification of specific features in the steel microstructure related to carbide coarseness. Quantitative carbon concentration profiles were obtained by GD‐OES to evaluate the decarburization effect on the microstructure of low‐carbon steels considering different initial microstructures. The effect of the spatial distribution of carbides in these microstructures on the decarburization kinetics was also studied. Through quantitative determination of carbon elemental profiles by GD‐OES, information about the morphology of the cementite in the microstructure and its development in relation to decarburization was acquired. The depth of decarburization can accurately be determined. On the basis of the global results, GD‐OES thus emerged as being a fast and reliable technique for a better understanding of decarburization kinetics. Copyright © 2015 John Wiley & Sons, Ltd.     

An effect of measurement conditions on the depth resolution for low‐energy dual‐beam depth profiling using TOF‐SIMS

An effect of measurement conditions on the depth resolution was investigated for dual‐beam time of flight‐secondary ion mass spectrometry depth profiling of delta‐doped‐boron multi‐layers in silicon with a low‐energy sputter ion (200 eV – 2 keV O₂⁺) and with a high‐energy primary ion (30 keV Bi⁺). The depth resolution was evaluated by the intensity ratio of the first peak and the subsequent valley in B⁺ depth profile for each measurement condition. In the case of sputtering with the low energy of 250 eV, the depth resolution was found to be affected by the damage with the high‐energy primary ion (Bi⁺) and was found to be correlated to the ratio of current density of sputter ion to primary ion. From the depth profiles of implanted Bi⁺ primary ion remaining at the analysis area, it was proposed that the influence of high‐energy primary ion to the depth resolution can be explained with a damage accumulation model. Copyright © 2013 John Wiley & Sons, Ltd.     

Analytic function to describe interfaces and resolution consistency in sputter depth profiling

A simple analytical function is derived to describe the interface shapes measured in sputter depth profiling by using X‐ray photoelectron spectroscopy or secondary ion mass spectrometry. This function involves the convolution of a central Gaussian function, often taken to describe the roughness, together with an exponential tail to describe mixing and an exponential approach often taken to describe an information depth. This model is consistent with Hofmann's mixing‐roughness‐information model that does the same by numerical analysis, but we present a direct analytical function that is more transparent to the user. The differential of the function gives Dowsett's function for delta layers. Depending on which of the 3 base parameters are identified as sample related, the analyst can obtain the centroid of the underlying composition. These functions are used to show the extent that the common measure of depth resolution for step edges and delta functions diverge as the profile becomes less Gaussian.     

Quantification of AES depth profiling data of polycrystalline Al films with Gaussian and non‐Gaussian surface height distributions

Sputtering‐induced roughness is the main distortional factor on the depth resolution of measured depth profiles, in particular, for sputtering of polycrystalline metals. Frequently, the surface height distribution of the sputtering‐induced roughness exhibits an asymmetrical feature. In such a case, a non‐Gaussian height distribution function (HDF) has to be applied for the quantification of a measured depth profile. By replacing the usually applied Gaussian HDF with that of an asymmetrical triangle in the Mixing‐Roughness‐Information depth model, measured Auger electron spectroscopy depth profiling data of the interface of polycrystalline Al films on Si are perfectly fitted. The asymmetric triangle height distributions obtained from the best fit are a reasonable approximation of the height distributions measured by atomic force microscopy. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel floating‐type low‐energy ion gun for high‐resolution depth profiling in ultrahigh vacuum

A floating‐type low‐energy ion gun (FLIG) has been developed for high‐resolution depth profiling in ultrahigh vacuum (UHV). This UHV‐FLIG allows Ar⁺ ions of primary energy down to 50 eV to be provided with high current intensity. The developed UHV‐FLIG was sufficiently compact, being ～30 cm long, to be attached to a commercial surface analytical instrument. The performance of the UHV‐FLIG was measured by attaching it to a scanning Auger electron microprobe (JAMP‐10, Jeol), the base pressure of which in the analysis chamber was ～1 × 10^?7 Pa. The vacuum condition of ～5 × 10^?6 Pa was maintained during operation of the UHV‐FLIG without a differential pumping facility. Current density ranged from 41 to 138 µA cm^?2 for Ar⁺ ions of primary energy 100–500 eV at the working distance of 50 mm. This ensures a sputtering rate of ～10 nm h^?1 with 100 eV Ar⁺ ions for Si, leading to depth profiling of high resolution in practical use. Copyright © 2003 John Wiley & Sons, Ltd.     

VAMAS interlaboratory study on organic depth profiling

We present the results of a VAMAS (Versailles project on Advanced Materials and Standards) interlaboratory study on organic depth profiling, in which twenty laboratories submitted data from a multilayer organic reference material. Individual layers were identified using a range of different sputtering species (C₆₀ⁿ⁺, Cs⁺, SF₅⁺ and Xe⁺), but in this study only the C₆₀ⁿ⁺ ions were able to provide truly ‘molecular’ depth profiles from the reference samples. The repeatability of profiles carried out on three separate days by participants was shown to be excellent, with a number of laboratories obtaining better than 5% RSD (relative standard deviation) in depth resolution and sputtering yield, and better than 10% RSD in relative secondary ion intensities. Comparability between laboratories was also good in terms of depth resolution and sputtering yield, allowing useful relationships to be found between ion energy, sputtering yield and depth resolution. The study has shown that organic depth profiling results can, with care, be compared on a day‐to‐day basis and between laboratories. The study has also validated three approaches that significantly improve the quality of organic depth profiling: sample cooling, sample rotation and grazing angles of ion incidence. © Crown copyright 2010.     

Preferential sputtering observed in Auger electron spectroscopy sputter depth profiling of AlAs/GaAs superlattice using low‐energy ions

Auger electron spectroscopy (AES) sputter depth profiling of an ISO reference material of the GaAs/AlAs superlattice was investigated using low‐energy Ar⁺ ions. Although a high depth resolution of ～1.0 nm was obtained at the GaAs/AlAs interface under 100 eV Ar⁺ ion irradiation, deterioration of the depth resolution was observed at the AlAs/GaAs interface. The Auger peak profile revealed that the enrichment of Al due to preferential sputtering occurred during sputter etching of the AlAs layer only under 100 eV Ar⁺ ion irradiation. In addition, a significant difference in the etching rates between the AlAs and GaAs layers was observed for low‐energy ion irradiation. Deterioration of the depth resolution under 100 eV Ar⁺ ion irradiation is attributed to the preferential sputtering and the difference in the etching rate. The present results suggest that the effects induced by the preferential sputtering and the significant difference in the etching rate should be taken into account to optimize ion etching conditions using the GaAs/AlAs reference material under low‐energy ion irradiation. Copyright © 2005 John Wiley & Sons, Ltd.     

Rapid quantitative analysis of fayalite and silica formed during decarburization of electrical steel

Subscales on surfaces are affected by the temperature and oxidation potential during decarburization annealing of electrical steel containing 3 wt% silicon. Knowledge of the structural and chemical properties of the surface oxide layer subscales permits the control of high‐temperature oxidation processes in the electrical steel. In the present work, the oxide layers were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry, and glow discharge optical emission spectrometry (GD‐OES). The main oxide compounds formed within the subscales during decarburization annealing of the electrical steel were fayalite (Fe₂SiO₄) and silica (SiO₂). The fayalite and silica contents were quantitatively determined by wet analysis via the galvanostatic electrolysis method, and these oxide content measurements were compared with the fayalite content determined by FTIR spectrometry and the silica determined by GD‐OES. The results determined by rapid methods and wet analysis showed good agreement. The present findings show that FTIR spectrometry and GD‐OES measurements may be used for the rapid quantitative analysis of fayalite and silica in surface oxide layers during the manufacture of electrical steel. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparison of depth resolution from a microscopically modulated Rh/C film after sputter profiling by SIMS and SNMS

Sputter depth profiles of an Rh/C microscopically modulated thin film (double layer thickness 7 nm) were obtained by low energy SIMS and SNMS. The depth resolution was obtained using the linear superposition of error functions at the interfaces. In optimal cases the depth resolution was shown to be of the order of 1–2 nm for both techniques.     

Surface characterization and depth profiling of biological molecules by electrospray droplet impact/SIMS

Electrospray droplet impact (EDI) was applied to the analysis of peptides. The etching rate of bradykinin was estimated to be ~2 nm/min. This value is about one order of magnitude greater than the etching rate for SiO₂ (0.2 nm/min). Considering that the etching rate of argon cluster ions Ar₇₀₀⁺ for organic compounds is more than two orders of magnitude larger than that for inorganic materials, the rather small difference in etching rates of EDI for organic and inorganic materials is unique. When water/ethanol (1/1, vol%) solution of gramicidin S and arginine was dried in air, [gramicidin S + H]⁺ was observed as a predominant signal with little [Arg + H]⁺ right after the EDI irradiation, indicating that EDI is capable of detecting the analytes enriched on the sample surface. Copyright © 2011 John Wiley & Sons, Ltd.     

Differentiation of 18O‐ and 16O‐rich layers in anodic alumina films by glow discharge time‐of‐flight mass spectroscopy

The performance of glow discharge time‐of‐flight mass spectrometry in isotopic differentiation is revealed using the distribution of oxygen isotopes ¹⁶O and ¹⁸O in barrier‐type anodic alumina films as a focus. Anodic alumina films comprising ¹⁸O‐rich layers of controlled thickness were formed by the appropriate combination of anodising of superpure aluminium in electrolytes enriched with ¹⁸O isotopes and of natural abundance of ¹⁸O isotopes. Analysis of the elemental depth profiles of selected ionic species, i.e. ¹⁶O¹⁸O, allowed determination of the locations of the ¹⁸O‐rich layers and the ¹⁸O/¹⁶O interface. Copyright © 2010 John Wiley & Sons, Ltd.