AVS 46th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS-MoM

Invited Paper AS-MoM6
Imaging of Particulates using Auger Electrons

Monday, October 25, 1999, 10:00 am, Room 6A

Session: Imaging and Small Area Analysis
Presenter: M. Prutton, University of York, UK
Authors: M. Prutton, University of York, UK
D.K. Wilkinson, University of York, UK
M.M. El Gomati, University of York, UK
M. Jacka, University of York, UK
M. Kirk, University of York, UK
Correspondent: Click to Email
The currently favoured methodology of scanning Auger microscopy uses UHV SEM systems equipped with field electron emission sources in the column and coaxial mirror or concentric hemispherical electron energy analysers to detect electrons of a selectable kinetic energy. One technological objective is to produce digital maps in which the pixel intensities are proportional to the atomic fractions of the element giving that Auger line in the electron spectrum. This is significantly more difficult than simply acquiring and displaying signals proportional to the height or area of that Auger line because of the dependence of the Auger yield upon the local angle of incidence, the varying composition of sub-surface material and the presence of sharp changes in composition in the vicinity of the current pixel. Most of these difficulties have been removed or minimised in the York Auger microscope (MULSAM). The principal features of MULSAM will be outlined together with a short introduction to the methodology used to combine images obtained from several different scattered electron detectors around the sample. Examples will be given for correction of topographical artefacts in chemical maps and the use of multi-variate statistics to assist in the analysis of particulate catalysts. One disadvantage of current SAM designs is that sequential data acquisition is slow for multi-element samples. A new hyperbolic field analyser (HFA) will be reported that can acquire simultaneously an entire 1024 channel spectrum. It opens the way to obtain entire spectra in each pixel of an image. This could lead to very powerful methods of surface microanalysis using different parts of the spectrum in each pixel to correct for the local topographical and sub-surface composition. Some examples of spectra obtained from particulates using an HFA will be given. The outline design of a spectrum-imaging Auger microscope (SISAM) will be presented.