Ultimate Lateral Resolution in Electron Microscopy by FE-Auger

Pieter Bouckenooge, Herman Terryn, Isabelle Vandendael

Onderzoeksoutput: ChapterResearch

Samenvatting

A lot of modern day scientific developments and improvements find their origin in superior material selection compared to their preceding equivalents. For the majority of cases, the more appropriate material selection is enabled by a better handling, processing and understanding of the used materials. The surface characteristics are of key importance for many materials and their applications. Several physical and chemical properties can be altered by adjusting the surface of the material. Some important examples are: the scratch resistance of the surface; the colour of an object; the possibility to use a material as a catalyst via a larger contact area; the reactivity of solids for chemical processing and their inactivity as protection against corrosion. All the previous applications are governed by the characteristics of the first few micrometres of the material. Whenever the material’s chemical properties play an essential role, only the first few atomic layers will define its behaviour since only the surface atoms will primarily interact with the environment. To characterise these top layers, instruments with an analysing depth of a few nanometres are required. This excellent depth of analysis is provided by techniques such as ToF-SIMS, XPS and AES.
When looking at the upper atomic layers of a material, inhomogeneities in the lateral chemical distribution are not uncommon. To analyse these lateral distributions in the top surface layer a technique is required which combines an excellent depth of analysis and lateral resolutions, both in the nanometre range. Techniques like ToF-SIMS and XPS do not offer the necessary lateral resolution to characterise these inhomogeneities. The only common surface analysis technique which combines both nanometre scale lateral resolution and analysis depth is Auger electron spectroscopy (AES) combined with a field emission electron gun (FE). The required depth of analysis is obtained via the Auger effect, which is a three-electron effect and will only emit a detectable Auger electron from the atoms in the first few nanometres of the surface. The lateral resolution is obtained by focussing the incident beam. By the use of a field emission electron gun the primary electron beam can be focussed in a (sub)nanometre spot size.
In this review paper the FE-AES technique will be briefly compared to other well-known surface analysis techniques to emphasise the power of the FE-AES technique. Additionally, an overview of the currently commercially available equipment will be presented. Subsequently separate sections of the chapter will discuss important topics like: the analysis of coatings via a FE-AES system; the comparison of characterising conductive and non-conductive surfaces pointing out the challenges linked with specific surfaces; the opportunities of surface Auger electron spectroscopy mapping... In all these sections special attention will be given to the advantage of using the supreme lateral resolution of the FE-AES technique through well-established works and recent case studies.
Keywords: FE-AES surface analysis, lateral resolution
Originele taal-2English
TitelMicroscopy and imaging science
Subtitelpractical approaches to applied research and education
RedacteurenA. Méndez-Vilas
Plaats van productieBadajoz Spain
UitgeverijFormatex research center
Pagina's640-654
VolumeMicroscopy book Series
Uitgave7
ISBN van geprinte versie978-84-942134-9-6
StatusPublished - 1 feb 2017

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