Auger electron spectroscopy environment

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

Size reduction of metal particles results in several changes of the physico-chemical properties. The primary change is observed in the electronic properties of the metal particles which can be characterized by ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS, respectively) as well as Auger-electron spectroscopy (AES) measurements. Furthermore, morphology of the metal nanoparticles is highly sensitive to the environment, such as ion-metal interaction (e.g. metal-support interaction)... 

The elemental composition, oxidation state, and coordination environment of species on surfaces can be determined by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. Both techniques have a penetration depth of 5-20 atomic layers. Especially XPS is commonly used in characterization of electrocatalysts. One common example is the identification and quantification of surface functional groups such as nitrogen species found on carbon-based catalysts.26-29 Secondary Ion Mass spectrometry (SIMS) and Ion Scattering Spectroscopy are alternatives which are more surface sensitive. They can provide information about the surface composition as well as the chemical bonding information from molecular clusters and have been used in characterization of cathode electrodes.30,31 They can also be used for depth profiling purposes. The quantification of the information, however, is rather difficult.32... 

We next discuss x-ray absorption studies. To put matters in context, it is useful to understand that conventional studies using Auger electron spectroscopy (AES) and x-ray photoemission spectroscopy (XPS) can be carried out only ex situ in high vacuum after electrochemical treatment since the techniques involve electron detection. X-ray absorption spectroscopy can, in contrast, be used for valence and structural environment studies. As x-rays only are involved, they can be carried out in situ in an electrochemical or similar cell. 

Castle (LI, 12) and McIntyre (5) have shown how X-ray photoelectron spectroscopy (XPS or ESCA) can be applied to corrosion problems and uses of Auger electron spectroscopy (AES) in corrosion have been given by Clough (18, 19) and Thomas et al ( 0). Possible uses of ion beams in corrosion studies were presented by Deamaley (JU). Raman spectroscopy (.22, 23) and ellipsometry (19) are not discussed in detail in this paper, but they offer the advantage of allowing in situ measurements in a wide variety of corrosive environments. 

In situ methods permit the examination of the surface in its electrolytic environment with application of the electrode potential of choice. Usually they are favored for the study of surface layers. Spectroscopic methods working in the ultra high vacuum (UHV) are a valuable alternative. Their detailed information about the chemical composition of surface films makes them an almost inevitable tool for electrochemical research and corrosion studies. Methods like X-ray Photoelectron Spectroscopy (XPS), UV Photoelectron Spectroscopy (UPS), Auger Electron Spectroscopy (AES) and the Ion Spectroscopies as Ion Scattering Spectroscopy (ISS) and Rutherford Backscattering (RBS) have been applied to metal surfaces to study corrosion and passivity. 

Angle-resolved Auger electron spectroscopy ARAES Auger electrons are detected as a function of angle to provide information on the spatial distribution or environment of the excited atoms (see AES). Composition... 

Auger electron spectroscopy is used mainly for determining the elemental composition of the outer layers of a solid. Each element, when excited by the ionization of an inner electron level, emits Auger electrons with energies characteristic of that element and virtually independent of the chemical environment of the atom concerned. 

Fig. 2. Auger electron spectroscopy depth profiles for FA 49 a) exposed for 50h to environment 2 at 700°C, b) preoxidized for 16 h and exposed for 50 h to environment 1 at 700 °C...

Porous anodic alumina is a very promising material for nanoelectronics. The injection of different types of impurities inside an alumina matrix can substantially improve its electrophysical properties. It is very important to study the local environment (chemical bonds, electronic structure, etc.) of injected atoms for understanding physical principles of the electronic elements formation. A number of techniques can be used to determine a chemical state of atoms in near surface layers. The most informative and precise technique is X-ray photoelectron spectroscopy. At the same time, Auger electron spectroscopy (AES) is also used for a chemical analysis [1] and can be even applicable for an analysis of dielectrics. The chemical state analysis of Ti and Cu atoms implanted into anodic aliunina films was carried out in this work by means of AES. 

Auger electron spectroscopy with depth profiling via argon ion etching (position and thickness of near-surface layer), transmission electron microscopy of ultramicrotomed cross-sections (physical internal structure), elemental analysis (extent of metal salt conversion), and surface electrical resistivity versus temperature profiles (continuity of near-surface layer). The data from these techniques were used cooperatively to develop a model for these microcomposite polyimide films. The model represents the sample as three distinct regions. Fig. 1. The bulk of the film contains either converted (e.g. Ag) or nonconverted (e.g. C0CI2) additive in a predominately polyimide environment. An oxide-rich (e.g. 0 ) or metal-rich layer (e.g. Ag, Au) interspersed with polyimide accounts for the second region. 

Several analytical techniques which can be used to obtain information on the chemical composition of modified surfaces are available (58,59). For example, x-ray photo electron spectroscopy (XPS) can be useful for analysis of thin layers (to depths of 20 A) on substrates. XPS can provide both qualitative and quantitative information on the elements present as well as on their oxidation state, organic structure and bonding information. Auger electron spectroscopy (AES) is a similar technique, but offers only marginal information on the chemical environment of the elements. As for XPS, AES is a highly surface-sensitive technique. It is usually the outermost 2-6 atomic layers which are analysed. These surface-sensitive techniques are very prone to interference from absorbed contaminants. Careful handling of the sample between preparation in the electrochemical cell and the characterization experiment is therefore most important. AES is quantitative only to 50% (60). Electron microprobe analysis (EPMA) provides much more accurate quantitative data. 

If we assume that the development of a standard state, i.e. ideal metal-vacuum interface, was in fact the key to the advancements in metallic contact analysis we should also expect that this will also be the case in the polymer, or solid organic, friction or adhesion analysis. The consequence is that polymer surface characterization under various environments becomes the most important issue at hand. The achievement of the standard surface state in polymer or solid organic system will be most difficult due to the relatively weak intermolecular bonding forces and the normal existance of a wide range of impurities within the material itself. Ambient vacuum conditions are required for most of the physics oriented surface characterization techniques, e.g. LEED, FIM, Auger electron spectroscopy and under these conditions the surface can be modified by... 

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