Auger electron spectroscope surface sensitivities

As mentioned previously, this can be attributed in part to the lack of structure-sensitive techniques that can operate in the presence of a condensed phase. Ultrahigh-vacuum (UHV) surface spectroscopic techniques such as low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and others have been applied to the study of electrochemical interfaces, and a wealth of information has emerged from these ex situ studies on well-defined electrode surfaces.15"17 However, the fact that these techniques require the use of UHV precludes their use for in situ studies of the electrode/solution interface. In addition, transfer of the electrode from the electrolytic medium into UHV introduces the very serious question of whether the nature of the surface examined ex situ has the same structure as the surface in contact with the electrolyte and under potential control. Furthermore, any information on the solution side of the interface is, of necessity, lost. 

In order to obtain a fundamental understanding of oxide surfaces, well-ordered thin oxide films, grown in ultrahigh vacuum (UHV) under well-controlled (clean) conditions, has turned out to be a successful approach ([8, 17, 38] and references therein). In contrast to many (insulating) bulk oxides, thin oxide films exhibit electrical and thermal conductivity sufficient for the application of surface sensitive imaging (e.g., STM) and spectroscopic methods (e.g., XPS Auger electron spectroscopy, AES and temperature-programmed desorption, TPD). 

Surface spectroscopy is the most common tool used to characterize and analyze surfaces. Assuming that a technique of sufficient sensitivity can be found, another major problem that needs to be addressed in surface spectroscopy is distinguishing between signals from the surface and the bulk of the sample. It is important that the spectroscopic technique chosen be surface specific. The technique must be able to distinguish between signals from the bulk and the surface phase. To illustrate this, we shall look at one way in which surface specificity can be achieved that makes use of the special properties of low energy electrons. It is an approach employed in common surface spectroscopic techniques such as Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS). 

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