Low-energy Electron-induced X-ray Spectroscopy Research Articles

LEEIXS and XPS studies of reactive unbalanced magnetron sputtered chromium oxynitride thin films with air

Chromium oxynitride thin films were deposited onto polished carbon substrates by an unbalanced magnetron sputtering in a reactive atmosphere of argon and air with different relative humidities (concentrations of water vapor). The composition and thickness of chromium oxynitride thin films were measured by ion beam techniques such as: Rutherford backscattering spectroscopy (RBS) and resonant nuclear reaction analysis (RNRA). The nitrogen and hydrogen profiles were determined by RNRA and Tof-SIMS, the chemical bond analysis was carried out by low energy electron induced X-ray spectroscopy (LEEIXS) and X-ray photoemission spectroscopy (XPS). The LEEIX spectroscopic studies analysis have shown that, during metallic sputtering mode, the composition of CrNO can be fitted only by Cr 2O 3 with low content of CrN and CrO 2, and in the compound sputtering mode the CrO 2 stoichiometry predominates in the presence of low content of CrN. XPS results have also indicated the existence of another compound with (CrO 2) 3–N stoichiometry.

Study of CrN bonding in nitrided stainless steel coatings by low-energy electron induced X-ray spectroscopy (LEEIXS)

Thin nitrided stainless steel coatings (400–500 nm) were deposited onto polished low carbon steel substrates by magnetron sputtering in a reactive atmosphere of argon–nitrogen mixture. A series of coatings were deposited with a total gas-flow constant while increasing nitrogen proportion. The nitrogen content which was determined by nuclear reaction analysis (NRA) was found to increase with increasing N 2 flow-rate. The chemical bond between chromium and nitrogen was controlled by low-energy electron induced X-ray spectroscopy (LEEIXS) with a wavelength dispersive spectrometer equipped with a TlAP crystal (2 d=2.576 nm). The low-energy sub-band generated by the bonding between chromium and nitrogen allow us to determine the proportion of nitrogen contained in the coatings.

Speciation of inclusions and precipitates in steel by means of XRF and LEEIXS

AbstractFundamentals of x‐ray fluorescence spectrometry and X‐ray emission spectrometry in the case of electron probe x‐ray microanalysis and low‐energy electron induced x‐ray spectrometry are compared. The different aluminum and titanium compounds occurring in steel can be investigated by examining soft x‐ray spectra, arising from valence shell orbitals. The non‐metallic inclusions were isolated by galvanometric electrolysis. In the case of the speciation of titanium, direct electron bombardment of the sample is used to generate soft x‐rays. By investigating the Ti L lines, titanium carbide, nitride and sulfide can be distinguished. To specify aluminum compounds, the Kβ transition in the x‐ray fluorescence spectrum was examined. The concentration of aluminum oxide and nitride in precipitates of special steel qualities can be determined with a satisfactory determination limit. Finally, pre‐operational studies for the determination of different silicon inclusions using electron excitation were carried out. Copyright © 2003 John Wiley & Sons, Ltd.

Surface analysis of some polymer-based materials by means of a soft X-ray emission technique

This paper reviews the performances and limits of low-energy electron-induced X-ray spectroscopy (LEEIXS) in the surface and thin film analysis of polymer-based materials. The major interest of this soft X-ray emission technique results from the use of a windowless gas discharge tube operating in the primary vacuum of the X-ray spectrometer as an electron excitation source (1-5 keV). The capabilities of LEEIXS are illustrated through the analysis of light elements (C, O, F,Si, etc.) (i) in thin polymeric films deposited on metallic substrates from various wet (dipping, electrodeposition, electropolymerization) and dry (plasma polymerization, thermal evaporation) processes and (ii) on polymer substrates subjected to chemical or physical surface treatments. These examples also show that LEEIXS analysis, when it concerns organic or polymeric materials, is limited to those materials which present a sufficient chemical and thermal stability, as the electron beam bombardment, in spite of the low current density (0.1 mA cm-2) used, can cause degradation of many materials.

Calix[4]arene sensitive thin films for detecting sodium. Surface studies

In this work, we present experimental results about electrolyte–insulator–semiconductor (EIS)-type sensors based on evaporated p-tert-butylcalix[4]arene sensitive thin films devoted to sodium detection. Several calixarene films of different thicknesses (10–1000 nm) were studied and a significant decay of their detection ability was pointed out for thick samples. To investigate the presence of sodium encaged in the sensitive receptors, during the contact with the electrolyte, two surface analytical methods were used, namely, Rutherford backscattering spectroscopy (RBS) and low energy electron induced X-ray spectrometry (LEEIXS). Both methods show that sodium is incorporated within the membrane and that its surface concentration decreases as the calixarene film thickness increases, due to the growth of microcrystallites in the thickest films as pointed out by atomic force microscopy (AFM) observations.

UV laser photodeposition of carbon nitride thin films from gaseous precursors

We report on the synthesis of carbon nitride thin films using ArF excimer laser ( λ=193 nm) irradiation of acetylene and ammonia gaseous mixtures. The influence of the precursor composition on the nitrogen incorporation in the films was investigated by different techniques, namely X-ray photoelectron spectrometry (XPS), low-energy electron induced X-ray spectrometry (LEEIXS) and IR spectrometry. Scanning electron microscopy was used to characterise the microstructure of the deposited films. As shown by XPS the N/C atomic ratio varies by changing the precursor composition and reaches a maximum of 0.75 for a flow rate ratio NH 3:C 2H 2=5:1. Nitrogen as revealed by Fourier transform infrared spectrometry (FTIR) is single or double chemically bonded to carbon. The morphology of the deposited films investigated by scanning electron microscopy (SEM) depends also on the deposition parameters.

Characterization of Precipitates in Ti-Stabilized Steels with Low-Energy Electron-Induced X-Ray Spectrometry and Scanning Electron Microscopy

Various kinds of precipitates can influence the mechanical properties of Ti-stabilized steels. The qualitative composition of the Ti inclusions can be characterized microscopically, whereas for quantitative information to be obtained time-consuming selective dissolution must be used. The present study aims at chemical speciation of the isolated precipitates as a solid phase with the help of soft-X-ray spectrometry. Whether the method is capable of giving both qualitative and quantitative information on the composition of Ti-mixtures is discussed. The precipitates in Ti-stabilized steels are investigated after chemical dissolution of the steel matrix with a bromine/methanol mixture (1:10). By combination of soft-X-ray spectrometry with X-ray fluorescence (XRF) and scanning electron microscopy (SEM) both qualitative and quantitative characterization of the precipitates can be performed. They were found to consist mainly of TiC and TiN.

Catalytic combustion of methane: surface characterization of manganese-substituted barium hexa-aluminate catalysts

In order to achieve a good activity with respect to methane combustion, a good route would be via catalysts incorporating transition metals. For devices operating at high temperatures, such as gas turbines, substituted hexa-aluminates present the advantage of good thermal stability when compared to impregnated Al2O3. For the purpose of this study, manganese-substituted hexa-aluminates were prepared either by the sol–gel method or by carbonate precipitation. Surfaces were analysed by soft x-ray emission, namely low-energy electron-induced x-ray spectroscopy (LEEIXS), and by photoelectron spectroscopy, namely x-ray photoelectron spectroscopy. The results on samples incorporating increasing amounts of manganese show the existence of an upper limit to the number of atoms substituted at the catalyst surface. This limit is about 2.7 manganese ions per unit cell, for samples prepared either by the sol–gel or by the carbonate precipitation technique and then calcinated at 1200°C. The interpretation of the Auger parameter variations shows that the relative amount of Mn in oxidation state III increases when the surface amount of Mn increases, as well as with the Mn substitution level. This fact can be related to an increased activity for methane conversion. © 1998 John Wiley & Sons, Ltd.

Effect of the nature of the working gas on the d.c. magnetron sputter deposition of chromium nitride and oxi-nitride thin films on steel substrates

Chromium nitride and oxi-nitride films were deposited on low carbon steel substrates by d.c. reactive magnetron sputtering with Ar as the sputtering gas and N 2 or NH 3 as the reactive gas (the two gases entering the reactor via two separate inlets in order to avoid cathode poisoning). The effects of different experimental parameters, such as the power density, pressure in the reactor and substrate bias, on the film composition and structure were studied. Stoichiometric or near-stoichiometric CrN coatings were easily obtained in the amorphous or crystalline form depending on the bias voltage applied to the substrate. In contrast, oxi-nitride films were more difficult to obtain because of the high reactivity of oxygen compared with nitrogen. This difficulty could only be overcome by using a very low oxygen flow rate which was provided by the water vapour adsorbed on the reactor walls when the reactor was brought to atmospheric pressure by the introduction of air. Under these conditions, oxi-nitrides of reproducible composition were obtained. The film composition was investigated by X-ray emission spectrometry (X-ray fluorescence spectrometry (XRFS), low energy electron induced X-ray spectrometry (LEEIXS)), X-ray photoelectron spectrometry (XPS) and X-ray diffraction (XRD).

Adhesion Science and Surface Analysis. Typical Examples

Abstract A number of surface modification methods using mechanical, chemical, electrochemical or physical processes have commonly been employed to treat adherend surfaces and improve adhesion in various bi- or multi-layered systems which play a key role in many advanced technologies. Results reported in this review paper deal more particularly with components of polymer-metal systems and provide typical examples of surface analysis obtained by x-ray photoelectron spectrometry (XPS), ion scattering spectrometry (ISS), low-energy electron induced x-ray spectrometry (LEEIXS), optically stimulated electron emission (OSEE) and Fourier transform infra-red spectrometry (FTIR). These examples concern, on the one hand, metallic adherends (aluminum, stainless steel, zinc-coated steel, gold) the surfaces of which were modified by cleaning, etching, oxidation, conversion or chemical grafting and, on the other hand, bonded joints (polyester-steel and epoxy-aluminum systems) which were delaminated using a peel test and a three-point flexure test, respectively.

Silanization of Stainless Steel Surfaces: Influence of Application Parameters

Abstract The adsorption of y-aminopropyltriethoxysilane (y-APS) onto stainless steel substrates has been investigated by Low-Energy Electron Induced X-ray Spectrometry (LEEIXS). Results reported in this work show the influence, on the film thickness, on the one hand, of silane concentration, pH, aging time and alcohol/water ratio of the y-APS solution, and on the other hand, the influence of the drying conditions of the silane films. Clearly, these demonstrate the capabilities of LEEIXS for quantifying the amount of y-APS adsorbed on the metallic surfaces from the silane solutions. Some correlations are also shown between spectrometric results and mechanical data (practical adhesion measurements) provided by a three-point flexure test.

Department of Applied Chemistry and Chemical Engineering, Claude Bernard University (Lyon I): Current Research in Adhesion Science

Abstract This paper reviews the activity in adhesion science of the Department of Applied Chemistry and Chemical Engineering (CNRS, URA 417) of the University of Lyon, France. This work essentially concerns treatments and modifications of surfaces by various chemical, electrochemical and physical techniques-electropolymerization, plasma polymerization, sol-gel processes, phosphatation, etc. Examples of the characterization of these surfaces and that of bonded joints are shown. Emphasis is placed on the possibilities offered by the techniques developed in the laboratory (low-energy electron-induced X-ray spectrometry and the three-point flexure test).

Study of nitrogen distributions implanted at high temperature into aluminum

Nuclear reaction analysis is a powerful tool for the study of nitrogen implantation into aluminum. Previously this technique was used for studying the depth distributions of molecular nitrogen implanted in aluminum at 100 keV to different doses, but at temperatures below 400°C. The aim of the current work is to study the processes involved when nitrogen is implanted at the same energy but at higher temperatures, between 400 and 550°C. It is found that at these temperatures, a nitrogen surface peak is present in the aluminum. In addition, the chemical bonding of nitrogen atoms with the aluminum matrix has been investigated by low energy electron induced X-ray spectroscopy (LEEIXS), which confirmed the formation of aluminum nitride at low implantation doses. The distribution of the C, O, 14N and 15N atoms at the surface has been measured by secondary ion mass spectroscopy (SIMS). It was found that the nitrogen surface peak is located close to the contaminated layer, which can be explained by nitrogen diffusion from the bulk to the surface followed by a precipitation in that region.

Recent Developments in Surface and Thin Film Analysis using Low - Energy Electron Induced X-Ray Spectrometry (LEEIXS)

AbstractA review is given of the main gas-discharge sources and auxiliary equipments which were used in soft and ultra-soft X-ray emission spectrometry. Special attention is paid to the basic principles and instrumentation of low-energy electron-induced X-ray spectrometry (LEEIXS) whose excitation source is an electron beam generated in a glow-discharge system. Capabilities of LEEIXS in surface and thin film analysis and characterization are illustrated by examples dealing with control and optimization of surface treatment and thin film deposition processes. Sensitivity of the technique down to the submonolayer range and influence of backscattering phenomena are shown.

X-Ray Studies of Chromium Nitride (CrxNy) Thin Films Deposited by Reactive Magnetron Sputtering

AbstractChromium nitride hard coatings have been prepared by a plasma process by varying nitrogen partial pressure. The crystallographic structure of these samples has been investigated by XRD and their chemical composition and stoichiometry by Low Energy Electron Induced x-ray Spectrometry (LEEIXS).

Low-Energy Electron Induced X-Ray Spectroscopy (LEEIXS), An Emerging Technique in Surface and Thin-Film Analysis. New Developments and Applications

Within the last two decades analysis and characterization of surfaces, interfaces and very thin films have become of considerable importance in many fields of modern technology. This increasing demand has lead to a rapid development of various surface and near-surface analytical techniques. Some of these methods such as XPS, AES, SIMS and ISS have matured both with respect to instrumentation and methodology and therefore are now sufficiently well-established. Others are yet in their infancy but possess a large potential and this is the case of low-energy electron induced x-ray spectrometry (LEEIXS) discussed hereafter.The instrument is a wavelength-dispersive x-ray spectrometer in which the conventional x-ray tube has been replaced by an electronically stabilized gas-discharge source. Such a system operates as an electron source under the primary vacuum of the spectrometer (≃ 10−1 torr). Typical operating conditions are in the range 0.5-5 kV with a current of 0.1-0.5 mA and the diameter of the electron beam at the sample surface is less than 1 cm2.

Titanium-base coating on plane silica substrates

Plane silica substrates were coated with a titanium-based deposit by gaseous cementation at temperatures ranging from 600 to 800 ° C, over 1 h to several tens of hours. The cement consisted of hydrogen chloride and titanium. The bilayer structure of the coating was established by X-ray diffraction, X-ray electron microprobe analysis, scanning electron microscopy, low-energy electron-induced X-ray spectroscopy. X-ray photoelectron spectroscopy, optical microscopy and X-ray fluorescence spectroscopy. Thin coatings were amorphous and the composition of the outer zone was close to TiO. Thicker coatings ranging from 2 to 30 μm were crystalline. In this case, the outer layer, designated α-Ti(O) or TiO x with 0.44 ⩽ × ⩾ 0.49, corresponded to an ordered solid solution of oxygen in a close-packed hexagonal titanium. The inner layer in contact with the substrate was Ti5Si3. At fixed temperatures (600, 650, 700, and 800 ° C), the thickness of the coating increased according to a parabolic law. Activation energy and diffusion coefficient were calculated. Thermodynamic considerations concerning the interactions between the gaseous phase of cementation and the silica substrate, are presented from theoretical calculations and from Ti-Si-O phase diagrams experimentally constructed at 800, 1000 and 1300 ° C.

Temperature and dose dependences of nitrogen implantation into aluminium

It has been established that nitrogen implantation into metals can alter their surface properties such as friction, wear, corrosion, etc. Recent studies have shown that nitrogen implantation into aluminium leads to the formation of aluminium nitride which has interesting tribological, electronic and optical properties. For a given implantation energy, the characteristics of the nitrogen profile, e.g. thickness, shape and concentration, depend strongly on the experimental conditions during the implantation. In order to study the influence of the implantation parameters, aluminium samples have been bombarded with 15N + 2 of 100 keV to different doses ((1–20) × 10 17 N +/cm 2), at several temperatures (25–300° C). Distributions of the implanted species were investigated by nuclear reaction analysis (NRA) and by Rutherford backscattering spectroscopy (RBS). The chemical bonds of aluminium in the matrix were studied by using low-energy electron-induced X-ray spectroscopy (LEEIXS). It is shown that aluminium nitride is formed and that the nitrogen distribution presents a surface peak when the implantation temperature is higher than 200° C.

Non-Destructive Chemical-State Analysis of Thin Films and Surface Layers (1-1000 nm) by Low-Energy Electron-Induced X-ray Spectroscopy (LEEIXS)

AbstractThe penetration depth of 1-12 keV electrons in most materials is less than one micron and the characteristic soft x-rays that are produced can be used to identify the elements present in the surface. Varying the energy of the incident electron beam enables the depth of analysis to be controlled.Soft x-rays often exhibit large 'chemical effects' (changes in peak profile and peak position) which can he correlated with chemical changes. A study of such effects for each element present in the sample surface, as a function of electron-beam energy, can in some cases, permit changes in the chemical state (valency - coordination number-spin state etc.) to be determined as a function of depth.Such analyses can be carried out either in a conventional x-ray spectrometer in which the x-ray tube has been replaced by a gas-discharge source, or in a spectrometer in which the sample is bombarded with electrons from a normal electron gun. In this paper these techniques are outlined and some applications reviewed:- the analysis of oxide layers on aluminium and steel, the analysis of aluminium-nitride layers produced by MOCVD on gallium arsenide, the analysis of silica fiims (with added boron and phosphorus oxides) on silicon and the analysis of zinc-oxide films on glass.

Surface characterization of AISI 304L stainless steel subjected to various prebonding treatments. Correlation with adhesion measurements

AbstractIn order to promote strong and durable steel/epoxy adhesive joints, various stainless steel surface treatments are investigated. The adherend surface characterization is achieved by both spectroscopic (low energy electron‐induced x‐ray spectrometry (LEEIXS), AES, XPS) and microscopic (SEM) techniques. The strength of the steel/epoxy bonds is evaluated, after bonded sample ageing under hydrothermal conditions (70°C, 95% r.h.), by means of a mechanical three‐point flexure test, sensitive to the interfacial properties of the bonded systems.The stainless steel surface treatments used in this study include conventional ones, such as solvent degreasing, acid etching, and phosphating and more original ones such as anodizing in sulphuric‐chromic or nitric acid electrolytes. These two last treatments lead to the formation of a ‘thick’ (in the range 10 to 90 nm) surface layer, highly chromium (as Cr(III))‐enriched, as determined by LEEIXS and XPS.The anodized stainless steel/epoxy systems exhibit performances which largely outclass those allowed by conventional steel prebonding treatments. These performances are very dependent upon the electrochemical conditions (current density, treatment duration, electrolyte temperature and composition) chosen for the anodizing process.