Basic Auger electron spectroscopy

Passivation of active metals to hydrogen reaction has been recognized as an important problem in basic metal-hydrogen studies, especially in their technological application to various situations. Few investigations have addressed these difficulties. The advent of modern surface analytical techniques such as photoelectron spectroscopyy Auger electron spectroscopy, and ion spectrometry offer a tremendous opportunity to attack the passivation question. Each of these techniques is discussed with regard to their capabilities and application to hydride kinetics. 

Benninghoven, A. Rudenauer, F.G. Wemer, H.W. Secondary Ion Mass Spectrometry Basic Concepts, Instrumental Aspects, Applications and Trends, John Wiley and Sons New York, 1987. Briant, C.L. Messmer, R.P., Eds. Auger electron spectroscopy. In Treatise on Materials Science and Technology, Academic Press, Inc. San Diego, CA, 1988 Vol. 30. 

Before discussing these aspects we have to clarify the state of BP on the surface of the positive electrode material. We measured the depth profile of thecobalt positive electrode after 200 cycles by Auger electron spectroscopy (AES), as shown in Fig. 19.18. Thickness of the electroconductive membrane (ECM) film is estimated by the AES depth profiles atomic concentration of cobalt and oxygen. It reaches 90% with and without BP addition as shown in Fig. 19.18. The observed ECM film thicknesses are as follow in the basic electrolyte, the ECM film thickness was 45 A in the functional electrolyte containing 1% of BP, the ECM film thickness was 68 A in the functional electrolyte having 2% of BP, the ECM film thickness was 214 A. These results clearly show that the ECM film thickness on the positive electrode increased with the amount of BP. Based on these results, the cycle life of the basic electrolyte cell should be better, but the cells with the functional electrolyte containing the small amount of BP (the film thickness of 68 A) afford the best results. 

From the large number of experimental methods employed currently in the analysis of surfaces (see, e.g., Morrison (1977) and Blakely (1975)), X-ray electron spectroscopy (XES), angle-resolved photoelectron spectroscopy (ARPES) and Auger electron spectroscopy (AES) are the ones which are most widely used for the study of the electronic states of the external layers of refractory phases. Their basic ideas and technical details are described in a number of monographs, see for example Nemoshkalenko et al (1976), Gallon (1981) and Briggs and Sinha (1987). 

Auger electron spectroscopy and x-ray photoelectron spectroscopy are probably the two surface analysis techniques that have found the greatest use in corrosion-related work. One of the first applications of surface analysis techniques to corrosion was an examination of the composition of the passive film on stainless steel. This investigation was undertaken to rationalize the substantial improvement in resistance to pitting and acid solutions that is found when Mo and/or Si are present in stainless steels. The AES results obtained in these early studies challenged the generally accepted explanation of the mid-1970s that the beneficial effects of Mo and Si were due to their enrichment of the passive film. In fact, the AES results indicated that Mo and Si were depleted in the film. There are basically two approaches... 

Of all the techniques that have been developed to analyze surfaces. Auger electron spectroscopy has had the most widespread application. In the field of materials science, it has joined such analytical methods as X-ray diffraction and transmission electron microscopy as a staple of any well-equipped laboratory. It is used in chemistry and materials science to study the composition of solid surfaces and the chemical states of atoms and molecules on those surfaces. Chemists and physicists study the basic Auger transition to help learn about electronic processes in solids. Those interested in developing electronic equipment have been concerned with providing spectrometers with ever-decreasing incident beam diameters that will allow the chemical analysis of a surface on a microscopic scale. It is hoped that this article plus the... 

The previous paragraphs give a brief introduction of the Auger process and the basic way in which surfaces are analyzed with it. However, the great power of Auger electron spectroscopy has been broad in its applicability. We now wish to discuss these applications in the field of materials science. 

This article has considered Auger electron spectroscopy. We have described the basic Auger transition, fundamental ways in which Auger electrons are detected, and various problems that can be encountered in using this spectroscopy. We have also considered the application of this spectroscopy in materials science. In the early days of the development of this technique, it was a specialized technique that was often the center of a particular study. 

While the same basic mechanisms for passivity of pure metals also applies to alloys, the processes involved in the passivation of alloys have an added complexity. In many cases only one component of the alloy has the property of being passive in a particular environment. Alloys such as steiinless steels, which contain highly passive components (chromium in this case), owe their corrosion resistance to the surface enrichment of the passivating component Thus stainless steels resist corrosion in many acidic systems (where iron or carbon steel would be poorly passive or not passive at all) by a passivating oxide film containing Cr predominantly as Cr(III). Surface analytical techniques such as Auger electron and X-ray photoelectron spectroscopies reveal substantial enrichment of chromium in the passivating oxide film on these alloys " . There are only two ways by which this enrichment can... 

NEXAFS spectroscopy basically does not require the most sophisticated apparatus to be performed but a source of tunable radiation as that dispensed by a photon factory or synchrotron plant. The experimental station for the study of macromolecular materials requires a UHV system and a detector apparatus for counting the emitted electrons. The primary process in NEXAFS is the core electron excitation into an appropriate final state empty molecular orbital. After excitation, the whole system undergoes relaxation and this can occur through two main decay processes secondary or Auger electron emission and fluorescence emission. Mostly, the detector for NEXAFS uses a simple channeltron tuned for a specific Auger energy or tuned to collect the whole secondary electrons resulting from the relaxation process fluorescence detector are also relatively common alternatively, for sample insulator the measurement of the drain current from the conductor sample holder is often measured examples are displayed in Fig. 4.4. Measurements can be performed on gas, solid and recently liquid state [3]. 

Tompkins (1978) concentrates on the fundamental and experimental aspects of the chemisorption of gases on metals. The book covers techniques for the preparation and maintenance of clean metal surfaces, the basic principles of the adsorption process, thermal accommodation and molecular beam scattering, desorption phenomena, adsorption isotherms, heats of chemisorption, thermodynamics of chemisorption, statistical thermodynamics of adsorption, electronic theory of metals, electronic theory of metal surfaces, perturbation of surface electronic properties by chemisorption, low energy electron diffraction (LEED), infra-red spectroscopy of chemisorbed molecules, field emmission microscopy, field ion microscopy, mobility of species, electron impact auger spectroscopy. X-ray and ultra-violet photoelectron spectroscopy, ion neutralization spectroscopy, electron energy loss spectroscopy, appearance potential spectroscopy, electronic properties of adsorbed layers. 

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