X-ray Induced Electron Spectroscopy Research Articles

A comprehensive SERS, SEM and EDX study of individual atmospheric PM2.5 particles in Chengdu, China

Characterization of atmospheric fine particulate matter (PM2.5) in large cities has important implications for the study of their sources and formation mechanisms, as well as in developing effective measures to control air pollution. Herein, we report a holistic physical and chemical characterization of PM2.5 by combining surface-enhanced Raman scattering (SERS) with scanning electron microscopy (SEM) and electron-induced X-ray spectroscopy (EDX). PM2.5 particles were collected in a suburban area of Chengdu, a large city in China with a population over 21 million. A special SERS chip composed of inverted hollow Au cone (IHAC) arrays was designed and fabricated to allow direct loading of PM2.5 particles. SERS and EDX were used to reveal the chemical composition, and particle morphologies were analyzed from SEM images. SERS data of atmospheric PM2.5 indicated qualitatively the presence of carbonaceous particulate matter, sulfate, nitrate, metal oxides and bioparticles. The EDX showed the presence of the elements C, N, O, Fe, Na, Mg, Al, Si, S, K, and Ca in the collected PM2.5. Morphology analysis showed that the particulates were mainly in the form of flocculent clusters, spherical, regular crystal shaped or irregularly shaped particles. Our chemical and physical analyses also revealed that the main sources of PM2.5 are automobile exhaust, secondary pollution caused by photochemical reactions in the air, dust, emission from nearby industrial exhaust, biological particles, other aggregated particles, and hygroscopic particles. SERS and SEM data collected during three different seasons showed that carbon-containing particles are the principal sources of PM2.5. Our study demonstrates that the SERS based technique, when combined with standard physicochemical characterization methods, is a powerful analytical tool to determine the sources of ambient PM2.5 pollution. Results obtained in this work may be valuable to the prevention and control of PM2.5 pollution in air.

Influence of Cluster Sources on the Growth Mechanisms and Chemical Composition of Bimetallic Nanoparticles

Metal nanoparticles are omnipresent in today’s applied and fundamental research. Both wet-chemical as well as physical procedures for their fabrication are well-established, where the latter is of particular interest as they supply surfactant-free particles. Particle growth has been investigated for several decades, but due to its complexity, involving kinetic and dynamic processes on various length and time scales, often only phenomenological rules of thumb are available. In this study, we report on bimetallic AgAu nanoparticles and demonstrate how the additional degree of freedom of the chemical composition can be used to derive information about how and where the particles grow, depending on two different cluster source types (hollow magnetron vs laser vaporization). The chemical composition is quantified on the single-particle level using electron-induced X-ray spectroscopy (STEM-EDS) and shows significant differences for the two fabrication routes. Based on molecular dynamics and Monte Carlo simulations, we derive that for hollow cylindrical sources both the mean particle size and the chemical composition are determined within the plasma region, where particles not only grow but also evaporate low-boiling silver. The comparably large plasma plays a decisive role here, as opposed to planar magnetron or laser vaporization sources, where no such evaporation is observed. These results shed light into the complex cluster growth and help understanding and optimizing nanoscale fabrication processes.

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.

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.

Möglichkeiten der Röntgenfluoreszenz- und Röntgenemissions-Spektrometrie in der Werkstoffanalytik

The principles and applications of X-ray fluorescence spectrometry and X-ray emission in the electron microprobe analysis and low energy electron induced X-ray spectrometry were described. With the help of soft X-ray spectra, arising from the valence bands, the different aluminum and titanium compounds of precipitates in steel can be investigated. The precipitates were isolated by an galvanostatic electrolysis. For speciation of aluminum the Kβlines in the X-ray fluorescence spectrum were investigated. The composition of aluminum oxide and -nitride in precipitates of special steel qualities can be determined. In the case of the speciation of titanium a direct electron bombardment of the sample is used to generate soft-X-rays. By investigating the L-lines of titanium different species like titaniumcarbide,-nitride or sulphide can be distinguished.

Depth profiles in nitrogen implanted Si xAl y coatings post-implanted with oxygen

“Sialons” are phases in the Si–Al–O–N and related systems based on the (Si, Al)(O, N) 4 tetrahedral structure. They have several interesting mechanical, thermal and chemical properties to make them candidates for high temperature applications. Thin Si–Al–O–N layers (200 nm) were synthesized using nitrogen and oxygen implantation into Si 33Al 67, Si 45Al 55 and Si 63Al 37 thin films deposited by d.c. magnetron sputtering on glassy carbon substrates. Nitrogen has been first implanted at 50 and 20 keV, then oxygen was post-implanted at 50 keV with doses ranging from 1 to 10×10 17 ions cm −2. High depth resolution profiles and stoichiometry have been obtained using Rutherford backscattering spectrometry and resonant nuclear reaction analysis. The chemical bonds have also been investigated using low energy electron induced X-ray spectrometry. Analysis of the results shows that the nitrogen concentration decrease when oxygen is post-implanted. Chemical bond analysis indicates the presence of a solid solution containing Si, SiO 2, Si 3N 4, Al, Al 2O 3 and AlN. The percentage of these compounds are correlated with the heat of formation.

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.

Adhesion Measurement of Amorphous C : H Films Deposited onto Stainless Steel. Spectroscopic Investigation of Interfaces

Abstract Amorphous hydrogenated carbon films obtained by the Plasma Assisted Chemical Vapor Deposition (PACVD) process, have been extensively studied by many authors1,2,3 because of their interesting properties (hardness, optical transparency, chemical inertness, high electrical resistivity). In the present work, carbon films were deposited on stainless steel from glow-discharge polymerization of methane at reduced pressure, using an RF generator operating at 13.56 MHz. These thin protective films are able to play the role of a primer to which another polymer (adhesive, paint, lacquer …) can subsequently be adhered. Surface treatments of the substrate and of the polymeric film were developed in order to obtain suitable adhesion properties, firstly of the film on the metal substrate, secondly of an adhesive on the hydrogenated carbon film. These treatments were monitored by two spectroscopic methods, viz. X-ray photoelectron spectroscopy (XPS) and (Low Energy Electron Induced X-ray Spectrometry) (LEEIXS). ...

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).

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.

Thermal Stability of CoSi2 on Single Crystal and Polycrystalline Silicon

ABSTRACTThe thermal stability of Co silicide on single crystal and polycrystalline Si has been investigated. Co films were evaporated onto (100) Si and undoped polycrystalline Si and annealed in vacuum. Resulting silicide films were examined using Rutherford backscattering spectroscopy, scanning electron microscopy, electron-induced x-ray spectroscopy, and sheet resistivity measurements. We find that CoSi2 on single crystal (100) Si remains stable through 1000°C. In contact with undoped polycrystalline Si, intermixing begins at temperatures as low as 650°C for 30min annealing. The Co silicide and Si layers are intermixed after 750°C 30min annealing, giving islands of Si surrounded by silicide material, with both components extending from the surface down to the underlying oxide layer. The behavior of CoSi2 contrasts with results reported for TiSi2 which agglomerates on single crystal Si around 900°C but is stable on polycrystalline silicon as high as 800°C. Resistivity measurements show that the Co silicide remained interconnected despite massive incursion by Si into the silicide layer.

Detection sensitivities in proton and electron induced X-ray spectroscopy

Both electron and proton induced X-rays can be used for analytical purposes. We have compared their relative sensitivities for detecting various constituents in a well characterized NBS low alloy steel standard. Both energy dispersive and wavelength dispersive spectroscopy were used in detection, and optimum beam energies were used in excitation. We find that for an equal accumulated charge the detection sensitivity by proton induced X-rays was a factor of two to three times greater than by electron induced X-rays for all elements. The increase of X-ray production by using proton energies above the level available to us (3 MeV) is rarely warranted in view of a corresponding increase of X-ray absorption losses in the target.

Analyse de films minces et ultra-minces: Perspectives nouvelles en spectrométrie d'émission des rayons X

This paper illustrates the capabilities of “low-energy electron induced X-ray spectrometry” (LEEIXS) for surface and thin, or ultra-thin, film analysis. The work deals with anodic films and shows that it is possible to measure oxide film thicknesses in a range between 0 and a few hundred angströms. In addition, it is demonstrated that this technique provides some information about the distribution of impurities in the interior of the films.

Detection sensitivities for thick specimens in proton and electron induced x-ray spectrometry

Detection sensitivities for thick specimens in proton and electron induced x-ray spectrometry