Substrate/surface characterization Auger Electron

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. 

When investigating adsorption phenomena a key requirement is to study the cleanliness of a given substrate before the adsorption process and to determine the chemical compositions of the products formed in the subsequent adsorption. For this purpose techniques which are sensitive to the presence of different elements on a substrate surface are required. Although virtually all of the methods discussed here can be used in one way or another to follow an adsorption process, a technique which provides direct information on the chemical composition of a surface is very often a necessary prerequisite for fully characterizing the behavior of a particular adsorption system. In the following we will discuss first secondary ion mass spectroscopy, or SEVtS, and then two variants of photoelectron spectroscopy. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). 

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